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THE PLANET 




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E. M. ANTONIADI 




THE PLANET MARS 

E.M. Antoniadi 

Translated by Patrick Moore 



Eugene M. Antoniadi was a Greek 
astronomer who spent most of his life 
in France, and was recognised as the 
foremost authority on Mars and 
Mercury. One of the most gifted 
observers of this century, he did 
much of his work with the great 33 
inch refractor of 53 feet focal length 
at Meudon, near Paris, He died in 
occupied France during 1939. 

This book is the English trans- 
lation of his own extensive work on 
Mars, originally written in 1930. It 
includes his observations of the 
Martian clouds and the so-called 
'canals', and much of his pioneering 
work is still useful. Of course, 
information sent back to Earth by 
recent rocket vehicles to Mars has 
shown that some of the author's 
conclusions were wrong; but none 
can fail to admire his careful, pains- 
taking work and his 140 excellent 
illustrations. 



ISBN 904094 14 6 



£15.00 
(U.K. only! 



f 



THE PLANET MARS 



THE 
PLANET MARS 

E. M.ANTONIADI 

Translated from the French 
by Patrick Moore 



KEITH REM) LIMITED 

SIIALDON DKVON 



ISBN O 904094 146 



© E. M. Antoniadi 1930. English 
translation Patrick Moore 1975. 
All rights reserved. No part of this 
publication may be reproduced, stored 
in a retrieval system, or transmitted, 
in any form or hy any means, elec- 
tronic, mechanical, photocopying, 
recording or otherwise, without the 
prior permission of Keith Keid Ltd. 



Printed and bound by W & J Mackay Ltd, Chatham 



CONTENTS 

Foreword 7 

PART I GENERALITIES 

i The Planet in Antiquity 1 1 

2 Instruments and Stations 14 

3 Astronomical and Physical Constants 20 

4 The Patches on the Surface 25 

5 The Illusion of the Canals 33 

6 The Snowy Polar Caps 47 

7 The Atmosphere of Mars : 

It's Clouds and Winds $2 

8 Physical Conditions and Habitability 65 

9 The Two Satellites of Mars 7° 

PART 2 TOPOGRAPHY OI ; .MARS 

Introduction 79 

1 Mare Tyrrhenum, Syrtis Major and Sinus Sabaeus 86 

2 Margaritifer Sinus, Aurorae Sinus, Solis Lacus and Mare 
Boreum 168 

3 Mare Sirenum and Mare Cimmerium 231 

4 The South Polar Zone 286 

5 The North Polar Zone 301 
Index 327 



Foreword 



E. M. Antoniadi, the Greek astronomer who spent much of his life 
in France and made extensive planetary observations with the great 
33m refractor at Meudon, was recognized as the foremost authority in 
connection with Mars and Mercury. He wrote books about both these 
planets. The Planet Mercury remained untranslated until 1970, when 
I produced an English version which ran through the periodical 
Astronomy & Space; subsequently it appeared in book form. I have 
therefore translated Antoniadi's much longer book about Mars, since 
despite the Mariner probe revelations the text and drawings are still 
of absorbing interest. 

As with the Mercury book, I have made absolutely no attempt to 
bring the text up to date, I have translated it just as Antoniadi wrote 
it in 1930. Of course some of his conclusions are now known to be 
wrong; but I do not think that anyone can fail to admire his careful, 
painstaking work. 

E. M. Antoniadi died in Occupied France during the war. He could 
not know that within a few decades rocket vehicles would have flown 
across space to Mars. Yet Antoniadi will always be remembered as one 
of the great astronomical pioneers who did so much to improve our 
knowledge of our neighbour planets. 

Patrick Moore 



PART i 

GENERALITIES 



The Planet in Antiquity 

Ancient Names, Symbol, Colour and Brilliancy of Mars 

The planet was known under the name of Harmakhis in Ancient 
Egypt, where it was also called Har decher, that is to say the Red One, 
because of its colour. 1 The Chaldaeans gave it the name of Nergal — 
the Babylonian Mars, the great hero, the king of conflicts, the master 
of battles and the champion of the gods; 2 and the planet was known 
on the banks of the Euphrates under the names of Allamou and 
Almou. 3 

The Greeks called it Ares (Mars), 4 name of the God of War, and 
apparently it was also known sometimes as Hercules.* Moreover, it 
was regarded as fiery 8 and impetuous. 1 Proclus Diadochus called it 
'celestial fire', and added that it symbolised fire. 8 The sign <J represents, 
so far as we know, the spear and shield. 

The Arabs, the Persians and the Turks named it Mirikh, which 
signifies a torch, iron, steel, and a long arrow thrown to a great dis- 
tance. It was also known in Persia under the name of Bahram and 
Pahlavani Siphir, or the celestial warrior. 

Among the Indians Mars was called Angaraka (from angara, burn- 
ing coal), and they also called it Lohitanga, the red body, from loliita, 
red, and anga, body. 9 Its astrological influence was regarded as being 
essentially malign. 

From Ares (Mars) and grapho (I design or write) the words areo- 
graphy, or geography of Mars, and areology, the geology of the planet, 
came into use during the last century. 

Plato, who at the end of his life was converted to the heliocentric 



11 



system of the world, discovered in Greece 2,000 years before Coperni- 
cus, 10 found the colour of Mars reddish, 11 and also very red. 1 *. It was 
naturally because of this burning colour, which is so vivid and which 
recalls the colour of blood, that the planet has been given the name of 
the God of War; and whenever the Greeks or the Romans spoke of a 
yellow, orange or reddish star, they never omitted to compare it with 
Mars. When near conjunction with the Sun, the planet seems to 
twinkle near the horizon, because of the smallness of its disk. 

For most of the time Mars shines in the sky as a star of the first 
magnitude, but it falls to the second when near conjunction. Its stellar 
magnitude is —1-85 at the time of mean opposition, and +i-6 at mean 
conjunction. When at unfavourable opposition, the magnitude falls to 
—it, below that of Sirius; but it attains —2-8 at the time of perihelic 
oppositions, 13 when it surpasses Jupiter in brilliancy — a fact which 
did not escape the notice of the ancients, because, according to Pro- 
clus, Mars 'seems more brilliant than Jupiter when it comes to peri- 
gee', 1 * At these times it is about 55 times brighter than when at its 
mean conjunction with the Sun, and in 1719 its brightness even caused 
a panic; many people believed that it was a temporary star (nova), or 
a red comet forecasting calamities for the human race. 

Ancient Observations: the Day of Mars (Mardi) 

The planet was observed in early times in Egypt, and then in China 
and in Assyria. By 2540 BC, the day Tuesday (French, Mardi) carried 
the name of Mars, Mortis dies in Latin. The Observations of Bel, writ- 
ten in cuneiform characters on tablets found in the ruins of Nineveh 
in Assyria, and dating back to at least the seventeenth century bc, con- 
tain a complete book dedicated to the planet. But the most ancient 
precise observation of Mars which has come down to us dates only 
from the 52nd year after the death of Alexander the Great — a date 
which corresponds to the 486th year of the era of Nabonassar, or 
272 bc. On 17 January of that year Mars passed close to the star Beta 
Scorpii, as is recorded by Ptolemy in his Mathematical Syntax. 

In the history of astronomy, Mars is celebrated because of the study 
of its elliptical orbit carried out by Kepler on the basis of the observa- 



12 



tions made by Tycho Brahe — a study which, as we know, led on to 
the discovery of the laws which regulate the movements of the planets. 

Occultation of Mars observed by Aristotle 

The great philosopher described his observation of this phenomenon 
as follows : 'We have observed the Moon, being at half phase, to pass 
under the star of Mars, which was hidden at its dark side and emerged 
on the bright side.* 15 

References 

1 G. Maspero. Histoire ancienne des peuples de I'Orient, 78. 

3 Ibid, 151 : Vigouroux, Dictiormaire de la Bible, vol IV, col 1603. 

3 Hastings, Dictionary of the Bible, vol III, 514, 1900. 

4 Plato, Epinomis, 987 c, and many other authors. 

5 Theon of Smyrna, ed Teubner, 130. Achille Tatius, however, said that the name 
Hercules was given to Mars by the Egyptians {Introduction mix Pkinomenes 
d'Aratus, 17). 

6 Cieomcdes, Cyclic Theory of Meteors, 1,3; and many others. 

7 Dorotheos, in the edition Teubner of Manetkon, 1 14. 

8 Commentary of Timon (Plato), III, 154* and i, 14B. 

9 Arago, Astronomie populaire, vol. IV, 135. 

10 For the discovery of the heliocentric system by the Greeks, see Bull. Astr. Soc. de 

France, vol. 41, 449-58, 191 7 and vol. 42, 166-9, 1928. 

1 1 Republic, I, 14. 

12 Epinomis, 987 c. 

13 These estimates of brilliancy are due to H. N. Russell, R. S. Dugan and J, C. 
Stewart in their excellent work Astronomy, vol 1, 335, 1927. 

14 Commentary on the allegory of Plato's Republic, 147. In 1924 M. Grenat drew my 
attention to the fact that Mars, near its perihelic opposition of that year, appeared 
more brilliant than Jupiter, and I was able to confirm this. 

15 Du Ciel, II, 12, 292. The expression that the Moon passed under Mars simply 
indicates that our satellite, being closer to us or lou-er in the heavens than the planet, 
passed between Mars anil the Earth. 



13 



Instruments and Stations 

Apertures of Instruments Most Effective in the Study of Mars 

The experience gained with all sorts of telescopes, with apertures 
ranging from o™-075 to i m -2$, has shown me — in agreement with 
Barnard and Hale— that for studying planetary surfaces, large tele- 
scopes are vastly superior to smaller ones. 1 This is in conformity with 
the laws of diffraction and the intensity of light. Thus, for instance, the 
om'83 Meudon refractor, when used for this kind of work, has the 
following advantages over instruments of moderate power: 

1 The apparently lesser distance or the object being observed, due 
to the greater separating and light-gathering power of the objective. 

2 The resolution of patches into fine structure.* 

3 The visibility of small new patches. 

4 The visibility of irregularities along the contours of those patches 
which at first sight appear regular. 

5 The increase in dimensions of faint spots, and the increase in 
breadth and intensity of a genuine blackish line, such as the Cassini 
Division in Saturn's rings. 

6 The gain in contrast of the image, and the greater intensities of 
patches. 

7 The visibility of irregularities in spots which, with smaller instru- 
ments, appear uniform. 

8 The visibility of faint half-tones, inaccessible to smaller tele- 
scopes. 

* For details of the separating power of various instruments, see the comments 
below on the canal illusion. 



14 



9 The better visibility of true colours, and the appearance of 
additional tints. 

10 The visibility of small imperfections of the image, such as the 
minor atmospheric undulations which, by the flow of diffraction, can- 
not be seen with moderate-sized telescopes — in which the rainbow 
effects of atmospheric dispersion persist up to an altitude of 30 above 
the horizon. 

However, atmospheric agitation frequently reduces the superiority 
of large instruments. Thus, during very transparent nights, with 
extremely unsteady images, the om-83 refractor will show the patches 
no better than an o m '30 instrument; in fact the patches are as well 
seen, by virtue of the greater light-grasp and separating power, only 
during moments of relative calm. This superiority becomes striking 
under misty conditions, and is overwhelming when images are really 
good. 

From a practical point of view, the undulations in the air act so that 
in general the power of a telescope increases rapidly up to o m, 2S aper- 
ture, following the law of separating power almost exactly; but it is 
not the same for greater apertures, and Burnham, using 0^-30, 0^-47 
and om*9 objectives, could not separate double stars down to Dawes' 
Limit, finding that performance fell below theory by from 15 to 60 
per cent. 8 It is true that Dawes's formula does slightly exaggerate the 
separating power of a telescope. However, bearing in mind the agita- 
tion of the air, it cannot be said that under normal conditions the 
Meudon o*n-83 refractor, with its perfect objective, is almost four 
times more powerful than the 0^-218 telescope used by Schiaparelli. 
With the best images, it reveals a host of minor details and coloura- 
tions absolutely inaccessible to the o m -30 or even an o« 1 *50 telescope ; 
but in my twenty years' experience I have had few nights with perfect 
images — on average, one in fifty. The best images of Mars I have had 
on Mars with the Meudon refractor were those of 20 September 1909; 
they remained perfect for over two hours. Although the magnification 
of 320 used at that time did not enable me to make full use of the 
separating power of the telescope, the aspect of the planet was a real 
revelation; in the middle of a crowd of irregular patches I saw, on the 



15 



site of one of Schiaparelti's linear, single or double 'canals', an ex- 
tremely broken-up lake; and the region to the south of the Syrtis 
Major presented the aspect of a field of fresh grass and woods of 
darker green, the whole area being dotted with tiny white points. 
There was no geometrical regularity in the innumerable details seen 
on this unique occasion ! 

Judged by the results obtained with the planets, the great Meudon 
refractor rivals those of Lick and Yerkes, whose apertures are respec- 
tively o m -o,i and im-02. 

The genius of Mr Ritchey has enabled him to construct the enor- 
mous, perfect i m '$z and z m, 57 mirrors at the Mount Wilson Observa- 
tory; these are the most powerful telescopes of our time. We know 
that with the first of them Mr Ritchey, penetrating much farther into 
the infinite than any of his predecessors, has been able to make a 
vitally important discovery — that of the remote spiral systems, 
thousands in number, analogous to our Milky Way. 

Use of Magnification 

The half-tones and the colours on planets are best seen with rela- 
tively low powers; for instance, 270 on the o m -83. Powerful eyepieces 
are necessary for examining the irregular contours of the patches, and 
for studying the truly whitish regions* and very high magnifications 
are essential for giving good views of the very faint satellites, where one 
must use the full separating power of the telescope. 

When making estimates of the changing reddish colours on Mars, 
it is important always to use the same low-power eyepiece. 

Here are the magnifications which can be used to advantage with 
the great Meudon refractor, under normal conditions: 

Sun, Mercury, Venus, Jupiter, globe of Saturn 270, 350 and 540 
Mars, Moon, ring of Saturn, Uranus, Neptune 270, 350, 540, 

810 and 1250 
Satellites of Mars, Uranus and Neptune 540, 810 and 1250 

Details on the satellites of Jupiter 540, Sio, 1250 

and 2500 



16 



Instruments: Various Considerations 

The passing of air-masses of different densities in front of the objec- 
tive, and in contact with it, continually changes the velocity of light 
in the air outside the objective and in the glass of the lenses. This 
results in a frequent change in the position of the focus, which it is 
important to follow by constant adjustment of the position of the eye- 
piece. 

Let us add that amateurs who are equipped with a good objective 
or mirror have a focus which is viturally fixed — that is to say, incapable 
of much adjustment. With the Meudon refractor, under good condi- 
tions and with a high magnification, the effects of moving the eyepiece 
by a tiny fraction of a millimetre are noticeable. When it is remembered 
that the focal length of the objective is very long — i6 m, i6 — this fact 
is evidence of the genius of the brothers Henry, the makers of this 
marvellous piece of optics and also great pioneers of celestial photo- 
graphy. 

I prefer refractors to reflectors; the secondary spectrum is not a 
serious disadvantage. The rest of the colours in a reflector are not 
perfect, because of the selective absorption of the silver on the mirror. 
The closed tube of a refractor leads to more stable images than does 
the open tube of a reflector. However, since LasselFs time we have 
found out how to improve the images in a reflector, by doing away 
with the tube and replacing it by an open framework. This procedure 
should be followed by all owners of reflectors. 

Finally, the great height of the Meudon objective above the ground 
(24m) is, according to Mr, Ritchey, an advantage — because at this 
height he considers that the atmospheric undulations are less of a 
nuisance. 

High-Altitude Stations 

It is evident that observatories situated at high altitude are better 
for astronomical work than those near sea -level, because the observer 
has less air above him, and therefore less atmospheric undulation. 
'The great Meudon refractor,' writes M. Emile Touchet, 'if taken to 
the advantageous height of the Haute Provence — found to be an excel- 



17 



lent site by M, Esclangon and later by MM Danjon, Coudert and 
Dufay — would give better results,' I agree entirely with this view 
expressed by my learned friend. Thus Flagstaff in Arizona, at an alti- 
tude of 2,210m, should be the world's premier astronomical station, 
because there is no observatory at a higher altitude at which work can 
continue throughout the winter as well as in the summer. But as each 
site — even Paris, with its fogs and smoke — can sometimes furnish 
perfect images in a large instrument, the supremacy of Flagstaff over 
Meudon, for example, is confined to the greater frequency of excellent 
images in so far as planets are concerned. The transparency of the air 
is not relevant. And as at Flagstaff there is the pernicious habit of 
stopping down the aperture for most of the time from om*6i to an 
average of om--j8, we have the paradox that at the times of best viewing 
Mars seems farther away than from Meudon, where the full aperture 
is used. It follows that the best images obtained from Meudon are at 
least twice as 'close' as those from Flagstaff. This advantage has been 
shown to be decisive; the photographs of Mars taken by Lowell at 
Flagstaff are not in accord with his drawings, but agree well with my 
drawings made from Meudon! One must never exaggerate the value 
of high-altitude stations and neglect the most vital factor; the indi- 
vidual quality of the observer. The fact that the 'canals' covering Mer- 
cury, Venus, Mars, Jupiter and its satellites, and Saturn, as reported 
from Flagstaff, rebel against the laws of perspective, and yet are 
regarded by their discoverer as so prolific,* confirms the truth of the 
theory which I am going to put forward; and it is ironical that the 
very worst planetary drawings have been made at the best observing 
station ! 

High-altitude observatories can give of their best only when they 
are equipped with telescopes as large as possible, and when these 
telescopes are used to their full capacity. 



• M. Douglass, who has drawn certain of the 'canals' at the Lowell Observatory, 
wrote in 1907 of the 'feeble illusions of canals . . . (which) have seriously affected the 
observations' (Pop. Science Monthly, vol 70, 174, 1907). This return to accuracy is 
greatly to his credit. As Faraday said: 'In science, one should criticise only the man 
who will never change his mind.' 



IS 



Meteorological Conditions Most Favourable for Images 

It is nearly always during light mist that the images are perfect in 
the o m -83. Cirrus gives results which are less good. In general, misty 
nights are calm and good ; but great transparency of the atmosphere, 
with brilliant, strongly-twinkling stars, visible almost down to the 
horizon, and above all an east wind, gives maximum agitation. How- 
ever, this is not an invariable rule; with the great refractor I have 
sometimes had tolerable images on transparent nights, and agitated air 
during a mist. On some occasions perfect images came suddenly after 
a period of light undulation, as though an agitated curtain or sail had 
been abruptly withdrawn. A high wind sometimes provides good 
images, as was also noted by Herschel and Barnard; and during the 
great heat-wave of 191 1 a strong, hot north wind allowed me to see 
Jupiter in great detail, though the image was never perfect, and there 
was a tendency for the agitation to increase noticeably as the night 
passed. An effect due to the dome was also noticeable. For about 
twenty minutes after opening the slit, the images at Meudon are 
generally good; then they tend to fall away. It was this dome effect 
which made Barnard say that he hoped the great Yerkes dome would 
be mounted on a rail, so that he could push it away and work in the 
open air with perfect images! Finally, it is worth noting that in day- 
time observation we have to reckon with cumulus, which seems to 
contain agitated air in a layer of variable thickness. 



19 



Astronomical and Physical 
Constants 



Numerical Data 
Mars is the fourth in the group of so-called terrestrial planets, in 
order of distance from the Sun (Fig i), and its orbit is outside that of 
the Earth. It can approach us closer than any other body apart from 
the Moon, Eros and Venus. Here are the various astronomical elements 
relating to our neighbour world: 

Mean distance from the Sun, Earth = i :i '52369 = 227,700,000km 

Perihelic distance = 1-3826 = 206,000,000km 

Aphelic distance — 1,6658 = 248,000,000km 

Least distance from the Earth at perihelic opposition = 56,000,000km 

Least distance from the Earth at aphelic opposition = 00,000,000km 

Revolution period = 66o| Martian days or 686-9797 Earth days ■ 686d 23I1 

3om 3 4is 
Orbital velocity (Earth's = 29-76km/s) = 24-nkm/s 
Orbital inclination to the ecliptic = i°si'i* 
Longitude of ascending node = 48 56' 30* 
Longitude of perihelion = 334° 35' 
Longitude of aphelion = 154 35' 
Position on the celestial sphere of Mars' north polar point = RA 317 , decl. 

+ 530 
Axial inclination to the perpendicular to the orbital plane (Hermann Strove 's 

value, derived from the movements of the satellites) = 25 s 10' 
Latitude of the Tropics of Leo and Aquarius = ± 25 10' 
Latitude of the polar circle = ± 64° 50' 
Longitude of the southern summer solstice, or the northern winter solstice 

= 356° 48' 
Longitude of the southern winter solstice, or the northern summer solstice 

= 1 76° 48' 



ISO 




— 0' 



Fig 1 The orbit of Mars, compared with those of the Earth, Venus and Mercury, 
In this figure, -n represents the perihelion and a the aphelion of each planet. E, in- 
dicates the spring equinox in the southern hemisphere of Mars (or the autumn 
equinox in the northern hemisphere); E 2 the soutliem autumnal or northern spring 
equinox. St is the southern summer or northern winter solstice; S, the southern 
winter or northern summer solstice 



20 



21 



Longitude of the southern autumnal equinox, or the northern spring equinox 

= 86° 48' 
Longitude of the southern spring equinox, or the norther autumnal equinox 

= 266° 48' 
Length of the southern spring, or northern autumn = 146 days 
Length of the southern summer, or northern winter = 160 days 
Length of the southern autumn, or northern spring =199 days 
Length of the southern winter, or northern summer =182 days 
Mean interval between opposition = 779 days = ayr 43d 
Rotation period (discovered by J. D. Cassini in 1665, who gave it as 24b. 40m) 

= 24I1 37m 22s 64 
Oblateness = 1/220 
Diameter (9**30 at unit distance), Earth = 1 (seen from Earth, the angular 

diameter varies between 3"6 ane 25"- 1, and, at oppositions, from 14*0 to 

25*- 1 ) = 0-528 = 6730km* 
Surface (Earth = 1) = CZ78 
Volume „ = 0*142 

Mass „ = O'io6 

Density „ = 0.71 

Density (Water = 1) = 3.93 
Gravity at equator (Earth = 1) = 0.38 = 3™*70 
Mean diameter of the Sun (Earth = 1) = 0*656 ( = 21' 2*) 
Mean light and heat received from the Sun, those received by the Earth being 

taken as unity m 0*43. (The range is between 0-52 at perihelion to 036 at 

aphelion.) 
Value of i" areocentric on the surface of Mars = 60km 



When near perihelic opposition, Mars is at its closest to the Earth, 
and its southern hemisphere is presented; at aphelic oppositions, when 
the planet is at its greatest opposition distance, the northern hemisphere 
is tilted toward us. 

The Phases of Mars 

Away from opposition, or conjunction with the Sun, Mars shows 
phases, discovered in 1 610 by Galileo not long after the invention of 
the telescope by Zacharie Jansen or Joannides.+ In a letter addressed 

" The most favourable opposition of Mars which has been systematically observed 
was that of 23 August 1524. On that date, the Earth made its closest approach to the 
orbit of Mars. 

T The name Joannides was a very common Greek name; thus it follows that the 
inventor of the telescope was a Greek, or at least a scientist of the Hellenic race. 



22 



to Father Castelli, dated 30 December 1610, the illustrious Pisan 
described his observation in the following terms: 'I ought not to 
assert that I can observe the phases of Mars; however, if I am not 
deceiving myself, I believe I can already see that it is not perfectly 
round.' 1 The phase is always gibbous; the part of the disk not illu- 
minated can never exceed \ of the diameter, ie 47 . Schroter correctly 
remarked that the phase shown by Mars is always a little less than the 
calculated value, because the true terminator is invisible due to the 
extreme obliquity of the solar rays falling upon it. 

The Albedo of the Planet 

Zoellner has noted that the variation in the light diffused by Mars 
according to its phases resembles that of the Moon." The planet 
reflects less than ~ of the light it receives from the Sun. Its surface 
is everywhere made up of lands and rocks which are less dark than 
those of Mercury or the Moon, but the albedo is much less than 
those of Venus and the giant planets, which are covered with thick 
clouds. 

The following table gives the approximate albedoes of the various 
planets; it represents a mean between the values given by Zoellner, 
Mueller and H. N. Russell: 



Venus: 0-65 
Jupiter: 0*5 
Saturn: 0-5 
Uranus: 0*5 



Neptune : 0*5 
Mars: 0*17 
Mercury: o-io 
The Moon : 0-09 



Here, for comparison, are the approximate albedoes of various 
terrestrial substances, after an examination of the results of Zoellner, 
Sumpner, Wilsing and Scheiner, and Graff, considered in the light of 

researches carried out by my distinguished colleague M. Bernard 
Lyot: 



Pure white chalk (Lyot's value), 0*79 
Freshly-fallen snow (thick later), 

0-78 
Cumulus, 0-71 
White paper, 0-70 



Basalt from Mandelstein, in Iceland, 

0-I2 

Lava from Buana, Cameroons, 0*12 
Syenite, 0-10 
Limestone, o*io 



23 



Pumice, 0-44 

Thin clouds, 0^37 

Granular chalk, 0-33 

White sandstone, 0-30 

Granite, 0-29 

Trachyte, 0*24 

Volcanic breccia, 0*2 1 

Red sandstone, 0-20 

Deserts (mean), 0-16 

Basaltic dole rite, coarse grain, 0-15 

Volcanic ash from Vesuvius, 0-14 



Basaltic lcucite, 009 

Wet cultivated soil, 008 

Trachytie lava, 0-08 

Basalt from Hvita, in Iceland, 0-08 

Lava from Vesuvius and Etna, 006 

Seas and lakes of pure water, 0-05 

Bumt pit-coal, 0-04 

Dark forests, 0-03 

Dark vitreous lava, 0-02 

Dark mat cloth, 001 

Black velvet, 0-004 






From these two tables, it may be deduced (1) that Venus, as we have 
said, shows a brilliancy almost equal to that of our cumulus; {2) that 
the surfaces of Jupiter, Saturn, Uranus and Neptune approach in 
reflecting power our clouds seen across an absorbing atmosphere such 
as that which obscures the disks of these bodies ; (3) that the surface 
of Mars shows an albedo similar to that of our dark reddish sandstones ; 
and (4) that the rugged surfaces of Mercury and the Moon have only 
feeble reflecting power, approaching those of our limestones, lavas and 
basaltic* rocks. 



References 



1 Arago, Astronomic populaire, vol IV, 126. 

2 Photontstriidie Untersuchmtgen, Leipzig, 1865. 



The Patches on the Surface 



The Reddish and Rosy Surface of Mars 

Mars is the only living world which has any analogy with the Earth, 
and whose true surface we can see, It is because of this that the study 
of the planet is so exceptionally interesting. The bright regions of 
Mars, known as continental regions, which occupy more than two- 
thirds of the total surface, are in general rosy or reddish in colour, 
interrupted by whitish or darker patches. The rosy tint is less obvious 
with diminution in the brightness of the disk, or behind light cloud; 
this is better studied with a large instrument than with a small one, and, 
as Arago has noted, 1 it vanishes — passing successively to orange, yellow 
and finally to a lemon tint — with the use of increased magnification. 

In many places the continental regions appear brightest in the 
equatorial region, at the border, and to the north of the dark patches 
which are known as maria. These bright regions, always rosy, and 
which seem to be particularly arid, are those which have been named 
Aeria, Edom, Aram, Chryse (east),* Memnonia, Zephyria and Aeolis. 
Farther north, the lands appear less rosy and more reddish — some- 
times even orange. The southern islands and the region lying to the 
south of the great dark patches often show up as red-vermilion ,with a 
broken, smoky colouration. 

John Herschel compared the red soil of Mars to our areas of red 
sandstone, 2 but the French astronomer Liais compared them with 
deserts of sand. 3 There is little to be said in favour of this hypothesis; 
however, small parts of these desolate regions — those which are pre- 
dominately of an accentuated red hue, such as Thaumasia, Aethiopis 

• The orientation used here is that of Mars ; telescopic east corresponding to Martian 
w est, and vice versa. 



24 



25 



and some of the southern islands of smoky vermilion colour — do seem 
to be deserts which may become temporarily fertile. 

The continental wilderness of the planet occupy an area almost ten 
times larger than that of our Sahara together with the deserts of Libya 
and Nubia. 

Dark Patches 

The dark areas of Mars, which can be seen with even a small telescope 
of aperture o ro *o5, and whose diffraction is perceptibly reduced in 
small instruments, give the general impression of being depressions. 
They show a range of colouration, decidedly variable; with reflectors 
they tend to look blue, while refractors show them as being green. It 
is worth noting that the southern hemisphere of Mars — part of which 
is occupied by the 'Great Diaphragm' of equatorial seas — everywhere 
shows an albedo lower than those of the bright rosy regions. An 
approximate north-west to south-east orientation is noticeable every- 
where, as if there has been former surface torsion. 4 To John Herschel, 
these areas were seas, 8 , water absorbing the light more strongly than 
the continents. However, John Phillips has noted that there is no solar- 
image reflection, 8 which, according to Sehtaparelli, ought in this case 
to show up as a starlike point of the third magnitude; and the colour 
alterations which are observed make HerschePs hypothesis untenable. 
The French astronomers Liais and Trouvelot much more reasonably 
attributed the extensive dark areas to vegetation, changing with the 
seasons; 7 but on Mars we can expect nothing more than xerophytic 
vegetation, similar, though not necessarily identical, with ours — and 
perhaps nourished in part by underground water supplies, 

The whitish borders which are seen everywhere along the edges of 
the dark patches are due to contrast; and it is for the same reason that 
the inner edges and the so-called bays sometimes seem blackish to an 
eye tired by prolonged observation. 8 

Changes m Extent and Colour of the Dark Regions 

The dark areas of Mars are stable in their mean outlines, but In 
places they are subject to important modifications in extent and 

26 






intensity. The reality of these changes, suspected by Father Secchi, 8 
was established by Flammarion; 10 they are of secular character in 
some cases, but may be irregular or seasonal. They consist of a 
decrease in albedo, or else of an invasion by the dark or greenish vegeta- 
tion on to the lightly-shaded or rosy areas adjacent to the great dark 
regions. 

Among the more remarkable secular modifications may be noted 
the exceptional development of the irregular streak of the Cyclops, 
and, in particular, of the region of Aethiopis between 1783 and 1800 ; 11 
that of the Hydaspes between 1858 and i87i; ia — to which I have 
drawn attention — in Ismenia, between 1837 and 1873 ; ia that of the 
Aurea Chersonesus, which showed great development in 1877 and 
1879; that of the Aonius Sinus, with the Pharsis, also in 1877 and 
1879 ;" the development of the Astaborae Sinus, in 1920-2, noted by 
M. Fournier; the very remarkable transformation of the Solis Lacus 
in 1926, which I recorded from my observations with the great 
Meudon refractor; 16 and, finally, the oblique darkening of the whole 
of the north part of Noachis in 1 928, the most extraordinary of all the 
metamorphoses observed on the planet. 19 

As examples of irregular changes, we may cite the broadening and 
abnormal intensity of the Nepenthes-Thoth in 1888, and again from 







.■ 




■ 


V^^ 8 ^ 


























wtc< 


-V 4 


«&£ 1 


' 












■ 






■ 






— •.."' 


. - i'-M 



Fig 2 Progressive discolouration of the greenish regions in the high 

southern latitudes of Mars, in 1924, indicating the change to brown. 

(p m -83 Meudon refractor) 



27 




Fig 3 Chart shotting the progress of the discolouration in the southern hemisphere 

of Mars, from 9 August to 15 September 1024. The figures indicate the dates when 

the patches were seen brown for tlie first time. (o m -8j refractor) 

191 1 to 1929;" that of the Pambotis Lacus in 1907 and ig^^ 18 and 
that of the Trivium Charontis from 1896 to 1899 and in 1924. 19 

As I have shown, the Syrtis Major shows up as narrow after peri- 
helion, broad after aphelion. 20 According to my data this is a definite 
seasonal variation; and the darkening of the Pandorae Fretum, taking 
place between heliocentric longitudes 230° and 10 , 21 and becoming 
most intense near perihelion, provides another example of change de- 

28 



pending upon the Martian season, though it is less regular than in the 
case of the Syrtis Major. 

Some of the dark patches, such as the Solic Lacus, the Nodus 
Gordii and certain streaks, seem more intense under oblique view than 
when on the central meridian. 

Correctness of the Vegetation Hypothesis 

In 1896-7 Lowell and Douglass noted that "as the dark areas of the 
southern hemisphere approached the middle of summer, from October 
to January, their colour changed from green to brown, then to yellow', 
and that 'this transition . , . resembles that of our vegetation during 
dry summers and in autumn'." This provides confirmation of the 
ideas of Liais and Trouvelot, which the American observers have cited. 
In 1924, using the Meudon refractor, I found however that the situa- 
tion is much more complex. I then saw a discoloration spreading out 
from the polar regions (Figs 2 and 3). It was originally detected on 
9 August, and was communicated to M. Baldet, who saw it on the 
following night: 10 August, Not only the green areas, but also the 
greyish or blue surface, turned under my eyes to brown, lilac-brown 
or even carmine, while other green or bluish regions remained un- 
affected (Fig 4). It was almost exactly the colour of leaves which fall 
from trees in summer and autumn in our latitudes. As for the dis- 
coloration of brown to yellow reported by Lowell and Douglass, I 
admit that I cannot confirm it ; it could be due to confusion with the 
yellow clouds of Mars. However, the brown colour comes sometimes 
early, sometimes late in the Martian year, and lasts for a short time, 
as with the brownish leaves of our vegetation. 

I have also seen the change in colour affect the irregular continental 
streaks. Thus the greenish tint of the Araxes and of the Tartarus be- 
comes a red-brown vermilion after long exposure to the almost zenithal 
Sun. 

Varied Nature of the Dark Patches. Absence of Seas on Mars, and 
Advancing Desiccation of the Planet 
The selective character of these changes has enabled me to establish 



29 




Fig 4 Chart of Mars, showing the colour changes observed in 1924. 
(o m -83 refractor) 



Patches turning from grey to green or brown 

Patches turning from green, grey or blue to lilac brown 

Patches becoming maroon 

Patches turning from grey to carmine 

Patches remaining green, unchanging 

Patches remaining blue, undianging 



that the dark areas of Mars are not all alike in nature, 22 and as the 
changes affect very large areas, I have proved by observation that on 
Mars there can be no seas comparable with our Mediterranean. There 
cannot even be large lakes. 23 Therefore Mars is undoubtedly in a state 
of desiccation incomparably more advanced than that of the Earth; 
and, as M. Puiseux- has remarked with regard to the Moon, the low 
density indicates porosity 24 and a gradual flowing of waters into the 
interior of the planet. But even if there cannot now be much water on 
the surface, this does not preclude the possibility of any water on Mars. 

Orogeny 

We have noted that on Mars we cannot expect the mountains to be 
high; they should be relatively lower than those of the Moon. Actually, 

30 



the terminator cannot be studied with certainty. Orogenic processes 
on Mars should be feeble, and this applies also to erosion by wind and 
water. However, the irregular streaks running from north to south, 
abutting on the equatorial seas, indicate differences in altitude and the 
basins of ancient rivers; and Flammarion has regarded as a moun- 
tainous region an eccentrically-placed spot near the south pole where 
deep snow accumulates in one place." Mr Campbell later put forward 
the interesting idea that the brilliant regions of the south polar cap, 
where the snow disappears more slowly than in the neighbouring areas 
— such as Argyre II, Thyle I, Thyle II and Novissima Thyle — are 
elevated plateaux. 28 The same should apply to Olympia, in the north 
polar region. This conclusion was supported by my 1924 observations 
at Meudon, when I saw the low yellow clouds extending across to the 
brilliant points in the southern hemisphere without covering them up. 

Vulcanism 

Volcanic phenomena certainly exist on Mars. But we have no visible 
proof—even though the frequent cindery aspect of the red land of 
Deucalionls Regio and the yellow atmospheric clouds may be mani- 
festations of it, and are in any case very enigmatical. 



References 



8 

9 
10 
II 

12 



Astronomie populaire, vol IV, 136. 

Outlines of Astronomy, 1876 edition, para 510. 

Cruls, Memoire sur Mars. Taehet de la plane te et dutie de sa revolution, 1878. 

For terrestrial analogies, see the admirable work by M. Puiseux, La Terre et la 

Lune, 38-47. 

Outlines of Astronomy, 1876 edition, 540. 

Proceedings of the Royal Society, meeting of 12 February 1863. 

Flammarion, La Planet e Mars, vol 1, 268; Comptes rendu* de t'Acadimie des 

Sciences, vol 98, 789, 1884. 

This is what 1 wrote in Knowledge, 247-8, 1903. 

Memoire deWOsservatorio del Coltegio romano, 17, 1863, 

Les Terres du del, 307 seq, 1876. 

This change was noted by van de Sande Backhuyzen (Flammarion, La Planete 

Mars, vol 1, 385). 

Noted by Schiaparelli (Flammarion, op cit, 447). 



31 



13 See my Mars Report for 1915-16, in BAA Mem, vol ai, IV, 88. 

14 Mars Report, 1896-7, BAA Mem, vol 6, III, 81. 

15 Butt de la Sac astr de France, vol 40, 409 and 512-13. 1926. 

16 Ibid, vol 43, 39-40, 1929. 

17 See my Mars Report for 191 I-I2, BAA Mem, vol 20, IV, 163-6. 

18 See my Mars Report for igo?, BAA Mem, vol 17, III, 90-1, and Bui. astr. soc. 
France, vol 38, 358-9, 1924. 

19 Bull astr soc de France, vol 38, 358-9, 10,24- 

20 See my note in Month. Nat. RAS, vol 76, 414, 1916. 

31 See my Mars Report for 1915-16, BAA Mem, vol 21, IV, 90. 

22 Fiammarion, La Planete Mars, vol II, 301. 

23 Bull de la Soc astr France, vol 38, 431, 1924; and vol 39, 81, 1925; Comptes 
rendus, vol. 179, 668-71, 1924. 

24 Bull de la Soar astr France, vol 38, 463, 1924. 

25 La Terre et la Lune, 111. 

26 La Planete Mars, vol I, 544, 



32 



The Illusion of the Canals 



Non-Existence of the Geometrical Canals: the Irregular Streaks of Mars 
The term 'canal' was introduced into areography by Secchi, to 
indicate the most important dark area on Mars, the Hourglass Sea or 
Syrtis Major. It was adopted by Schiaparclli to indicate the dark lines 
which he discovered in 1877-8, and which were glimpsed only for 
rare fractions of a second. However, the Italian scientist first used the 
term without drawing any conclusions as to the nature of the canals; 
it was only in 1895 that he identified them with true canals. 1 In fact, 
more or less straight, linear streaks had been shown on drawings of 
Mars made before those of Schiaparelli — notably on those of Herschel, 
Schroter, Kunowsky, Beer and Madler, de la Rue, Brodie, Secchi, 
Lockyer, Kaiser and above all by Dawes; but the Milan astronomer 
showed a much greater number of them in his drawings, and these 
numbers increased steadily until 1890, giving his 'canals' a more and 
more geometrical aspect. 

Some observers saw half-tones on the planet and did not differen- 
tiate between these and narrow lines; on the other hand some other 
observers turned half-tones into lines. Photography completely sup- 
ports the first view, not the second. In 1879 Green, a Very good 
observer and a talented draughtsman, put forward the idea that most 
of the 'canali* are the boundaries of pale greyish areas, a a view which 
has been subsequently verified. In 1886 Denning distinguished in 
these situations 'very feeble dark lines, with evident gradations in tone, 
and irregularities which here and there produce interruptions and 
condensations'. 3 This result was admirable in view of the fact that 



33 



it was obtained with an o m> 254 refractor. At the same time Thollon 
and Perrotin, at Nice, using an o m -j6 refractor, saw single and double 
lines, 4 confirmed in 1888 by Terby with an o m -20 refractor 5 and in 
1890 by Stanley Williams with an om-i6 reflector." In 1892 C. A. 
Young saw 'single irregular streaks, ill-defined and often discon- 
tinuous';' his observations, carried out with the powerful o ra, 58 
refractor at Princeton, left him very sceptical about the existence of 
rectilinear 'canals'. In 1894 Barnard studied the continental regions, 
and could see only details which were 'irregular and above all due to 
differences in tone', and 'no straight fine lines'. 8 In the same year, the 
same result was obtained by Laewy, Puiseux and Le Morvan with the 
great coude of the Paris Observatory. Also at this time, I in my turn 
confirmed the exactness of Schiaparelli's observations. With the o m -24 
refractor at the Juvisy Observatory, I everywhere saw single or double 
lines for an eighth of a second at a time. 

Also in 1894, Lowell and his assistants, W. H. Pickering and Doug- 
lass, drew an enormous number of 'canals', straight and rectilinear, and 
whose numbers steadily grew. Lowell interpreted them as bands of 
vegetation to either side of running water, so that they were narrow 
channels constructed by Martian engineers; the flow of water was 
controlled by numerous pumps, designed to make the water flow 
against gravity. At the same time Maunder — to whom Science was the 
most important contributor to the theory of the alleged 'canals' — 
wrote, with sound common sense: 'We cannot pretend that we can 
really distinguish the ultimate structure of the object we are examin- 
ing.' To him, the canals were 'the sum of a complexity of details'.* 
There was a wealth of meaning in those few words. Four years later, 
Cerulli put forward practically the same theory, and considered that 
the lines were due to the human eye, 'which makes the dark features 
run together to form a line', and for each canal pictured a 'mother 
band* on Mars, producing the illusion of a line. 10 Then, in 1903, 
Maunder proved in decisive fashion that young people who had not 
been warned drew lines upon a drawing which contained no canals. 
Millochau, assisted by M. Burson, successfully used the great Meudon 
refractor from 1898 to 1903 to distinguish, in the sites of the 'canals', 






'small dark patches with ragged borders, separated by non-tinted 
spaces,' various groupings of the patches often forming a 'string of 
beads'. With regard to the absence of rectilinear canals, M. Burson's 
impressions were identical with those of Millochau. Again, in 1903, 
M. Giacobini, discoverer of thirteen comets (including three periodical 
ones), observed Mars one evening under conditions of perfect images 
with the great o m -j6 refractor at the Nice Observatory, using a magni- 
fication of 800. He was struck by the rose colour of the continents and 
the fresh green of some of the dark patches, which gave him the im- 
pression of a terrestrial country landscape; and he could easily see 
several irregular streaks — but no geometrical structures or gemina- 
tions. In 1909, M. Frost declared that the Yerkes refractor was too 
powerful to show the canals. In 1910, Mr Hale wrote to me that in 
the previous year, using the marvellous i m, 52 Mount Wilson mirror, 
he had seen 'an enormous amount of detail* on the planet, so complex 
that he could not draw it, but 'with no trace of a geometrical reseau'. 
Mr Ritchey, who has studied Mars visually with the i m, 02 Yerkes 
refractor and the i m -52 Mount Wilson reflector, has told me that with 
the former instrument the details on the planet greatly resembled the 
irregular details shown in my drawings, but that the superior resolving 
power of his great mirror revealed a whole class of minor details, 
absolutely inaccessible to the Yerkes refractor; and that in neither 
case had he seen the slightest trace of geometrical structure. My 
observations made in 1909 with the o ra -83 Meudon refractor allow me 
to state that Schiaparelli's 'canals' have a basis of reality, but they do 
not exist on Mars as true canals, and they are not straight lines, either 
single or double (Figs 7 and 8). On 27 November 1909, Barnard wrote 
to me, among others: 'I am particularly glad that you have had the 
same view of the planet, and have drawn it with the great Meudon 
refractor. I note that in your drawings the canals have become broader, 
more diffuse and more irregular than most people show them. This is 
in accord with my own observations of the planet, made with large 
instruments.' My 1909 drawings were published in November of that 
year, 11 and Barnard had had enough time to compare them with his 
drawings and Mr Hale's photographs taken during the same period. 



34 



35 



On 1 6 May 1913, he wrote to me as follows: 'The very remarkable 
agreement between your drawing of the Syrtis Major region and the 
magnificent photograph by Mr Hale ought to interest every student 
of Mars. It proves to me that your drawings are precise.' Mr Hale also 
wanted to encourage me, and on 3 January 1910 wrote to me: 'My 
photographs are in excellent agreement with your drawings.' The 
examination of my 1909 results shows up a great variety in the struc- 
ture and aspect of the irregular bands. 13 Accordingly, I have found: 

1 That about 70 per cent of Schiaparelli's 'canals* are merely 
darkish irregular streaks, more or less continuous or ragged, broad and 
of different aspects; they are due to past convulsions in the crust of 
Mars. 

2 That about 21 per cent of the 'canals' are simply the broken 
borders of greyish areas ; and 

3 That about 9 per cent consist of single lakes, isolated and com- 
plex. 

In 1909, with the beautiful Henry objective, I saw the rectilinear 
'canals' disappear at the moment when very delicate details, beyond 
the range of Schiaparelli's or Lowell's refractors but confirmed by 
photography, became clearly and continuously visible. This is a 
fatal objection to the existence of the alleged geometrical reseau of 
canals — an objection which I formulated on 21 September 1909, the 
day after I made my first observations from Meudon. 1 * The same 
objection was raised quite independently by Mr Hale: 'If the 60-inch 
cannot show, in these regions of Mars, details smaller than those 
recorded by Lowell,' he wrote me on 3 January 1910, 'one can only 
assume either that the geometrical "canals" cannot be seen in so large 
an instrument, or else that the instrument itself is faulty. Yet I have 
always found that under the best atmospheric conditions, an aperture 
of 44 inches, or even more, is highly advantageous for the study of 
planetary details. I am also sure that from the optical point of view, 
the 60-inch is essentially perfect. , . . Under these conditions, the per- 
fectly "natural" aspect of the planet, and the total absence of straight 
lines or configurations such as those shown by Lowell, seems to me 
to be significant. I may add that observations of Mars with the 



36 



60-inch reflector have also been made by Abbot, Adams, Babcock, 
Douglass (not while at the Lowell Observatory), Ellerman, Fath, 
Scares and St John, all of whom agree with me with regard to the 
character of the details observed.' Finally, on 10 January 1910, Mr 
Hale wrote to Schiaparelli : 'My results (with the 60-inch in 1909) con- 
firm the conclusions I have reached as a result of my earlier researches, 
made with the 40-inch and the 12-inch at the Yerkes Observatory, and 
in agreement with the views expressed by Barnard, Campbell and 
Antoniadi. You will see that my photographs show no rectilinear 
"canals", and no aspect of geometrical structure.' 13 

On 27 May 191 o, Barnard wrote to me: 'Lowell seems to believe 
that large instruments cannot give definition good enough to show the 
geometrical canals. He forgets that the best proof of the power of 
definition of an objective is the separation of very close double stars. 
In this field, the work by Mr Burnham and Professor Aitken with the 
36-inch shows that measurements can be made of double stars which 
are so close that the Lowell refractor, under its atmospheric condi- 
tions, cannot hope to reveal.' Let us, therefore, give a summary ex- 
amination of this question of separation power. Dawes' limit, for 
stars of the 6th magnitude seen with good images, is 4*'56/a, where a 
is the aperture of the instrument in English inches. Thus an o m -025 
objective can separate two 6th-magnitude stars which are 4 #, 56 apart. 
On the other hand, Foucault has found that an o" 1 ^ can just split 
Gamma 2 Andromedae, where the separation is 4/10 of a second of 
arc. 14 Finally, slightly different results are obtained if one considers 
the most luminous part of the spectrum, around A = 5600. Here is a 
comparison of the figures obtained from the three formulae: (i) for an 
effective aperture of 1 centimetre, (2) for each of Schiaparelli's refrac- 
tors, and (3) for the Meudon objective: 





Full Aperture 




Separation Potter. 






of Instrument 


Dawes 


Foucault 


with X= 5600 




cm 01 


U*S8 


13*20 


14* jo 


Schiaparelli 


fo*2I 

\o- 4 8 


<>S5 
0-24 


063 

0-28 


C67 
0-29 


Meudon 


o-8i 


0-14 


0-16 


C17 



37 



As Burnham could never attain Dawes's limit with large apertures, 19 
it seems that Foucault's formula is preferable to that of the English 
observer, and this is in turn a little lower than the theoretical limit for 
longer wavelengths in the middle of the spectrum. 

The illusory nature of the rectilinear aspect of the 'canals' can again 
be demonstrated by diffraction, as follows: 

In Flammarion's classic work La Planite Mars, Vol. i, page 475, 
there is a drawing of the planet by Schiaparelli, dated 9 June 1910, 
where the blackish 'canal' of the Jamuna has a breadth of o**04. The 
instrument used had a separation power of o"-28. In Fig 5a, the breadth 
of the jamuna, MN = o"-04, narrowed by diffraction, should corres- 
pond to an increased true breadth OP = o*-i4 + o*-04 + o"-i4 
= o* , 32. Since the narrowing of a blackish band by diffraction is more 
or less equal to the power of compensation, the encroachment on the 
side of the band will be only half the whole width. Note here that in 
general, the intensities of so-called dark patches on planets are low, 
so that the encroachment of the light areas on to their edges is not 
noticeable. Since the separating power of the Meudon refractor is 
o**i5, the 'canal' in question, as seen with this objective on a disk the 
angular diameter of Mars, ought to have an approximate width of 
OP - OQ — RP = QR = o*-32 - (o*-o8 x 2) = o*-i6, that is to say 
about four times greater than Schiaparelli ! s line. Now, what is the 
appearance of the Jamuna in the great lens made by the Henry 
brothers? Nothing like a regular blackish streak four times as broad as 
Schiaparelli 's (Figs 5, b and c), but an irregular edge of a feeble half- 
tone (Fig 5d). (For the sake of clarity, the edges of the blackish streak 
C are not shown as graded in this diagram.) 
_Q_ M k n p 



Oil 



o*3 




B 

FigS 



38 






Thus, contrary to Lowell's ideas, the 'geometrical' canals are not 
real lines of dark parallel bands on Mars, since these would contravene 
the law of diffraction. They differ radically from a true black line, such 
as Cassini's Division in Saturn's ring, which is considerably broadened 
when seen with a large objective, in agreement with the law of diffrac- 
tion and with the separation of close double stars as seen in powerful 
instruments. 

Another fatal objection to the alleged reality of the rectilinear 'canals' 
has been pointed out by Maunder: 17 the 'canals' do not obey the laws 
of perspective. 

On page 424 of La PlanUe Mars, by Flamrnarion, there is another 
drawing of Mars, made on 2, 4 and 6 June 1 888. The 'canal' Euphrates- 
Arnon, which the Milan astronomer regards as the arc of a great circle, 
is there represented as in Fig 6. Knowing the direction of the north 
pole of Mars, OP (Fig 6b), the longitude of the centre of the disk 
to = 300 , and the latitude <f> = OE = +23 , nothing is easier than 
to calculate the orthographic projection of the eighth of the globe con- 
taining the 'canal' concerned, with the meridian and the parallels of 
latitude 15 from it (Fig 6b). Then, one rotation of this segment around 
the axis OP, bringing the 'canal' on to the central meridian, gives us 
for the Euphrates-Arnon the form shown in Fig 6c. 

Here, then, are the arcs of a great circle on the sphere when on the 
central meridian, so that each segment may appear rectilinear to the 
discoverer of the Martian 'canals' ! 

After what has been said, the term 'canal', applied to Mars, must 
indicate a hypothetical watercourse, straight and artificial, running in 
the middle of a band of vegetation with rectilinear, non-curved parallel 
sides. Let there be imaginary pumps, and optical streaks with straight 
edges and a mean breadth of 1 00 kilometres ; let there be bands which 
are real, irregular, more or less continuous; let there be extensive 
shading-off at their edges; and finally, let these lands be as vast as 
France or even India. The invention of the new terms necessary to 
describe this state of affairs will certainly enrich the language of 
science 1 

The great Meudon refractor has enabled me to clear up the question 



39 




Fig 6 Apparent form of the Euphrates- Arnon in June J 888 



of the 'canals' once and for all. Here is the actual truth of the matter : 
Nobody has ever seen a genuine canal on Mars, and the more or 
less rectilinear, single or double 'canals' of Schiaparelli do not exist 
as canals or as geometrical patterns; but they have a basis of reality, 
because on the sites of each of them the surface of the planet shows an 
irregular streak, more or less continuous and spotted, or else a broken, 
greyish border or an isolated, complex lake (Figs 7 and 8). ts Thus the 
details on Mars present everywhere a structure which is infinitely 
irregular and natural, so characteristic of the patches on all the bodies 
in the Solar System. 

'You have made great progress,' Barnard wrote to me on 15 October 
1 9 1 1 , 'in putting to the test a question so controversial as that of the 
canals.' These encouraging words were characteristic of this astro- 
nomer — a man as great for his personal qualities as for his scientific 
discoveries. 

It is necessary to add here that Schiaparelli's 'canals', which have a 
basis of reality, are quite different from the completely illusory 'canals' 
shown on the drawings made of Mars, and the other four planets 
known in ancient times, by Lowell and his assistants. It seems that 



40 



comparable canals on Venus, Jupiter and Saturn have been dug in the 
atmospheres of these planets ! Several authors have compared Lowell's 
charts of Mars sarcastically with spider's webs. Such a comparison 
is not inappropriate. This may not be entirely true of E.C. Slipher's 
'canals' seen at Flagstaff; but what can one think of the totally non- 
existent rescau of Triimpler, contradicted in the most categorical way 
by his own photographs, and allegedly seen — as we have noted — with 
the great Lick refractor: that refractor which Burnham considered 




Fig J 'Canals' : dark lines, single and double, glimpsed by Schiaparelli between 

18 '77 and i8go in the region of Elysium. (o m -2i8 and o m -i$o refractors) 
Fig 8 Resolution of the same details into completely irregular streaks and shadings, 
observed by the author in 1909, 1911, 1924 and 1926. (o m, #j refractor.) Figs 7 and 
8 show the rudimentary aspect and artificial appearance of the continental regions 
of Mars as seen with moderate telescopes, and the transformation into complicated, 
natural features when seen with the o m -3j Meudon refractor 

superior to that of Yerkes, and with which the keen-eyed Barnard 
never saw any straight features on the planet? The 'canals' of Slipher 
and Triimpler defy perspective; this is absolute and permanent evi- 
dence that they have absolutely nothing to do with real features of the 
planet. 

Let us add that this complex streakiness is peculiar to Mars, and 
is the result of past convulsions of the crust which occurred before the 
surface solidified, in agreement with the ideas of Descartes. Something 



4] 



of the same kind is seen on Mercury, and in a striking manner on the 
Moon, in the bright rays issuing from certain craters and in the valleys, 
clefts, crater-alignments, scarps, folds, terraces, dikes and chains of 
hills and mountains of our satellite. It is still evident on the Earth, in 
our valleys, cracks and faults, in our rivers, in the great depths of our 
seas, 19 and in our chains of mountains and islands. Thus, as Pcnard 
has commented, most of the irregular streaks on Mars correspond in 
general to our valleys. We can see something of the sort in the dunes 
of the Sahara. 

Optical Character of the Doubling of the 'Canals' and of the Lakes 

The fugitive aspect of the 'doubling' of the 'canals' and lakes on 
Mars was discovered by Schiaparelli in 1879, and seen by him at 
each subsequent opposition until 1890. The Italian astronomer called 
this new phenomenon 'gemination'. By the side of an existing 'canal', 
he claimed, another dark line might appear very rapidly, in a few days 
or even hours, parallel to the 'canal' and having almost the same in- 
tensity; in other cases the original "canal' would disappear, to be 
replaced by two parallel lines separated by an appreciable distance. 
Imagine the Seine suddenly disappearing, to be replaced by two dark 
bands, one of which would run from Dunkirk to Strasbourg and the 
other from Avranches to Lyons, and you will have an exact idea of 
what this second type of doubling on Mars would mean. In any case, 
I judged at an early stage that these phenomena were merely optical, 
and were impossible on the surface of the planet ; but this was not the 
opinion of their discoverer, who, not sufficiently appreciating the 
snares awaiting the observer at each stage in his work, continued to 
believe in the real existence of the rectilinear, variable, single or 
double and parallel bands on Mars: 'The polygonal arrangement and 
the geminations,' Schiaparelli wrote to me on 15 December 1909, 'of 
which you have such a horror (and which horror is shared by many 
others!) have in fact been confirmed so decisively that it is useless to 
protest, Dr Cerulli was convinced several weeks ago. I showed him a 
set of beautiful photographs taken by Mr Lowell in July 1907; he was 
able to see the doubling of the Gehon, the Ganges and several others. 

42 









I have myself seen the Agathodaemon, the Xanthus, the Euripus and 
several others which are more difficult. It seems that during the oppo- 
sition of 1909 no doublings were seen; I do not know what Mr Lowell 
found, as I have not yet seen his 1909 photographs. So far as I can judge 
from your beautiful drawings, the lines this time had the aspect which 
they normally showed in 1877 and, in particular, in 1879; bands of 
some considerable breadth, and irregularly speckled; no geminations; 
patches which were sometimes nebulous, sometimes decidedly con- 
fused. The remainder of the disk in 1879 showed great resemblance, 
in certain details, to that observed in 1909, The interval is 32 years— 
that is to say, a complete cycle; and this indicates that the aspect is 
likely to be similar. In fact: 

32 Earth years = 11,688 days 

17 Mars years = 11,679 days 

The difference is only 9 days. It therefore seems that the aspect of 
the lines and patches on Mars depends upon the position of the planet 
in its orbit, and that the period of this variation, as well as for many 
other phenomena, is almost exactly 32 years. From this it is permissible 
to conjecture that the geminations also obey this cycle, as do many 
other miracles of Mars.' 

The evidence of double streaks on the photographic plates would 
be of value only if all the images taken successively on the same night 
showed the traces; but this is not the case. Moreover, as the Flagstaff 
photographs had never done more than show the principal patches on 
Mars, if the double streaks which had allegedly been seen on the 
photographs were real, they ought to have been very striking to the 
eye when seen in a powerful instrument. Yet they were not even 
suspected. It follows that the so-called double streaks on the plates are 
due simply to the alignments of grains on the plates themselves. 
Nothing of the kind is shown on the best photographs of Mars which 
have ever been taken, those of Hale and Barnard. Moreover, Schia- 
parelli himself distrusted the details on the Flagstaff photographs. On 
29 August 1909 he wrote to me: 'Perhaps over a longer or shorter 
period, molecular actions develop inside the images, in spite of their 
being fixed — or even during the fixing— and these actions follow differ- 

43 



ent images of the same object, even when the photographs arc taken 
under conditions and circumstances which are apparently identical, 
and in the same series. All in all, the problem of the photography of Mars 
is beset with traps and difficulties.' In 1898 I established the optical 
nature of the geminations, which involves contrast phenomena and 
eye fatigue. I noted that the same 'canals' which appeared single to 
one observer would, at the same time, appear double to another; this 
happened also in 1886 with Schiaparelli, Thollon and Perrotin. The 
objection is unanswerable. Moreover, my observations at Meudon in 
1909, compared with the results at Milan, have shown that the doubling 
seems faint on each complex patch, and above all along the borders 
of irregular streaks, as can be seen from a further examination of Figs 
7 and 8. 21 These two drawings establish without doubt the optical, 
illusory nature of the straight lines and the geminations, and on this 
point completely refute the ideas of Mr. Stanley Williams. 

We can now make an accurate judgement of the work of Schiaparelli. 
This astronomer, already celebrated for his outstanding meteor work, 
has undertaken the study of Mars with very great perseverance, and 
in 1877, using his little o m, 2i8 refractor, was successful in noting the 
streaks or 'canals' which have everywhere a basis of reality; and as the 
planet was then close to the Earth, Schiaparelli was able to recognize 
numerous irregularities along the curves of these features. But during 
the following oppositions, from 1879 to 1886, Mars was farther away 
from us, and, because of diffraction, the irregularities in question be- 
came less and less recognizable; because of eye fatigue in addition, 
the streaks seemed to become thinner and to take on a more or less 
rectilinear or geometrical aspect. Then, in 1888 and 1890, the planet 
again approached the Earth," and as seen from Milan the irregularities 
reappeared, particularly since Schiaparelli was then using an instru- 
ment almost twice as powerful as his first; later, however, eye fatigue 
led on once more to geometrical patterns. Moreover, half-tones were 
seen more clearly because of the constant use of higher powers. Since, 
for rare instants of about | of a second each, I have myself seen the 
single or double optical lines, the accuracy of Schiaparelli's observa- 
tions is not in doubt. The error here has been in interpretation, not 

44 















observation; the Milan astronomer wrongly believed in the reality of 
the geometrical patterns on Mars, and excluded all possibility of illu- 
sion. Their miraculous character defied all explanation. As he wrote 
to me on 30 April 1900: 'Truly the planet has become a frightening 
and almost a distasteful subject to me. The more I study it, the less 
can I understand its phenomena.' 

This observer, Schiaparelli, has been a tutor to all of us; his great 
artistic talent; his very numerous original representations of Mars, sur- 
passing those of all other observers using instruments of equal aper- 
ture; the fact that his 'canals' correspond to details which are admit- 
tedly different, and yet are real; and finally his marvellous discovery 
of the slow rotation of Mercury with an objective of only o m -2i8 aper- 
ture, make him the foremost planetary astronomer of modern times, 
and a worthy successor to Jean Dominique Cassini. If he had had at 
his disposal a refractor as powerful as that of Meudon, our work there 
would have been rendered almost useless. 

Although I was absolutely hostile to all geometry in the structure 
of the Martian patches, and my views were thus diametrically opposed 
to his, Schiaparelli nevertheless carried on a friendly correspondence 
with me. 'As for my observations of Mars,' he wrote to me on 29 
August 1909, 'alas! I have made none since 1899. I must admit that 
the completely satisfactory observations, made under good atmospheric 
conditions with the full power of my left eye (the other is imperfect 
in some respects) ended in 1890. During the oppositions of 1892-4-7-9 
I still observed, but I made no drawings, because during this period no 
images were comparable with those of the period 1 877-9-82-4-6-8. In 
1892 I attributed this to the perpetual agitation of the atmosphere; the 
planet was low down, as was also the case in 1894. During 1894 (or 
1896) a deterioration in my eyesight was becoming more and more 
evident; the field of vision became darker and darker. At last, in 1900, 
I realized, with great sorrow, that the images were also becoming de- 
formed. Then, I made my farewell; I was in my 65th year. I also 
decided not to publish my observations of Mars made after 1890. My 
seventh Memoir, which deals with the opposition of 1 890, will be the 
last of the series ; it has been prepared for printing, and I hope to dis- 

45 



tribute the first copies next year. As for my observations made after 
1890, my notes and the few partial sketches which accompany them 
are kept in the Milan Observatory, where they may be consulted by 
anyone who needs them.' 

Optical Nature of the Apparent Roundness of the Small Patches 

The circular forms of the lakes on Mars which have been reported 
are as illusory as those of the geometrical patterns, because in 1896 I 
saw the lakes perfectly round even when a long way away from the 
centre of the disk. 32 In 1894 Maunder had already arrived theoretically 
at the same conclusion, noting with admirable acuity that large, com- 
plex spots on the Sun look generally round when seen with the naked 
eye ; and with our refractors, we see the patches on Mars under condi- 
tions very similar to those of sunspots seen without optical aid. 

References 



1 

2 
3 
4 
S 
6 

7 
8 

9 

IO 
II 
12 



13 
»4 
'5 
16 

J7 
18 



•9 

20 
21 

22 



Flamrnarion, La Planets Mars, vol II, 258-62. 
Ibid, vol I, 310—11, 
Ibid, 3 8g. 
Ibid, 301-4. 
Ibid, 419-21. 
Ibid, 470—3. 

Astronomy and Astro-Physics, vol II, 676, 1892. 

Month Not RAS, vol 56, 167, 1896; Flamrnarion, La Planets Mars, vol II, 237. 
Knowledge, 252, 1894; and 58, 1895. 
Marte nel 1896-j, 119. 

Bull de la Soc astr de France, vol 23, plates on 489, 1909. 

Comptes rendus de 1'Acad. Sci., vol 149, 836-8, 1909; Bull de la Soc astr de 
France, vol 23, 489 and 493-4, 1909; and vol 24, 34-5, 19 10; Athenae, 28 Septem- 
ber 1909. 

Rivisla di astranamia e scienze afini, vol 4, 114, 19 10. 
Annates de I'Observataire de Paris, vol V, 221, 1859. 
See above, chapter 1. 
See above. 

Knowledge, 250, 1894. 

Professor Pio Emanuelli of the Vatican Observatory, considered the comparison 
of my Figs 7 and 8 as 'a full disproof of the objective reality of the canals on Mars' 
{Conferenze e Psolusioni, vol 13, 404, 1920). 

This analogy with the fissures in our oceans is due to Svante Arrhenius (Le destin 
des itoiles, 144). 

Flamrnarion, La Planite Mars, vol. I, 580. 

See my Mars Report for 1909, in Mew. BAA, vol. 20, II, 44-5, 1915. 
Mars Report for 1896-7, ibid, vol 6, 89-90, 1898. 






The Snowy Polar Caps 



The Polar Snows of Mars 

These brilliant white patches were discovered by the illustrious 
J. D. Cassini in 1666. In a small instrument they appeared to project 
beyond the edge of the disk, a phenomenon explained by Bailly as 
being due to irradiation, 1 The eccentricity of the snowy polar cap was 
noted in 1720 at the Paris Observatory by Maraldi I., 2 and in 1877-9 
Schiaparelli found that the centre of the last trace of the southern cap 
was situated around 6° from the pole, or about 40 areocentric longi- 
tude. 8 The north polar cap seems to be less eccentric in position. 

The idea of attributing these polar whitenesses to snow was due to 
Herschel, who proposed it in 1784 because of their seasonal changes; 
they appear extensive in spring and continually shrink during the 
summer and autumn of each Martian hemisphere. 1 This theory of 
Herschel's is correct. Indeed, these white polar caps on the planet, 
which form during the long polar night, share with our Arctic and 
Antarctic icecaps the triple identity of position, of colour and of change 
which discounts the theory of Ranyard and Johnstone Stoney that the 
snowy caps of Mars are due to solid carbon dioxide. 

Arago has commented that the Martian snows are more than twice 
as luminous as the continents, 5 and this is true. It has also been rioted 
that the terrestrial-type clouds veiling Mars sometimes totally blot out 
the disk of the planet, leaving visible only the snowy polar cap in the 
guise of a small whitish patch. 

I have found that in general the southern snows are clearly observ- 
able between Martian heliocentric longitudes 240 and 75 , the 



46 



47 



northern snows between 6o° and 270 .* 1 The former accumulate during 
a longer winter, and can therefore become larger than the latter — to an 
areocentric arc of 60° at least, against about 50° for the northern 
snows.* We may suppose that the snows, exposed to the rays of the 
Sun, shrink by evaporation and melting. Arago considered that the 
lesser distance of the Sun at the time of the summer solstice in the 
southern hemisphere should make the southern snow melt more 
rapidly than the northern.' This is confirmed by observation. 

An examination of my drawings made since 1888, and comparing 
them with views of Mars obtained by other observers since 1856, has 
enabled me to draw up a time-table of the mean dimensions of the 
polar caps for different positions of the planet in its orbit. In the 
following table summarising these results, the second column gives, 
the altitude or the Sun above the Martian south pole (— ) or north 
pole(+). 



Heliocentric 


Altitude 


Diam of 


long, of Mars 


of Sun 


motes 






S 


N 








O 








-25 


14 


— 


10 


—24 


12 


— 


20 


— 22 


10 


— 


3° 


— 20 


9 


— 


40 


-l8 


8 


— 


5° 


-14 


7 


— 


60 


— ri 


6 


5° 


70 


-7 


5 


48 


80 


—3 


— 


46 


90 


+ 1 


— 


44 


100 


+5 


— 


42 


no 


+9 


— 


40 


120 


+13 


— 


37 


130 


+ 16 


— 


34 


140 


+ 19 


— 


31 


150 


+21 


— 


27 


160 


+23 


— 


24 



• The apparent size of the snowy areas is exaggerated by atmospheric agitation, and 
in small instruments, when Mars ia a long way away, by diffraction also — a trouble 
which is more of a nuisance in a small refractor than in a large one. 



48 



170 


+ 24 


— 


21 


180 


+25 


— 


18 


190 


+24 


— 


16 


200 


-2.2. 


— 


14 


210 


+ 20 


— 


12 


220 


+ l8 


— 


II 


230 


+ 14 


— 


10 


240 


+ 11 


60 


9 


250 


+7 


58 


8 


260 


+3 


56 


7 


270 


—1 


54 


6 


280 


-s 


SZ 


— 


290 


-9 


49 


— 


300 


—13 


45 


— 


310 


-16 


40 


— 


320 


-19 


34 


— 


330 


—21 


2V7 


— 


340 


—23 


22 


— 


350 


—24 


17 


— 



The albedo of these snows seems to be fairly high; 0-4 to o-6 as 
against o s 8 for ours. Moreover, their tones are varied — brilliant here, 
greyish there. Above all they are continuous, and their thickness must 
be slight — several millimetres at most — except on the high plateaux of 
Argyre II, Thyle I and II, Novissima Thyle and Olympia, where they 
may attain several centimetres. Probably their brightness is reduced, 
near their edges, by blades of grass and bushes. 

One very important fact, noted by Schiaparelli, is that the polar 
snow diminishes more rapidly on the dark areas than on the reddish 
soil. 6 It even seems to me that certain dark regions round the poles are 
refractory with regard to the ice ; 9 we may here have lakes and channels, 
as in our polar regions. Svante Arrhenius believed that warm spring 
existed in these areas. Let us add that we also have dark areas which 
are covered with the snowy mantle. Clouds floating above the Martian 
snows ought to hinder and retard their melting. 10 

Influence of Variations in Solar Radiation upon the 
Decrease of the Martian Snows 
Schain has had the idea that the changes in the intensity of heat re- 
ceived from the Sun ought to affect the sizes of the polar caps of Mars; 



49 



but in 1 912 he drew up curves and found that they were almost 
parallel for both caps between 1877 and 1907. 11 This is not all. Having 
examined the curves for the two caps since i860, I have found no 
parallelism whatsoever — particularly between 1877 and 1907 — but 
merely a simple general agreement with many irregularities. It is only 
in taking the comparison further that I have found an interesting re- 
lationship between the two phenomena. Near the exceptional solar 
minimum of 1913, the north cap of Mars was more extensive than at 
any time since 1856, according to the evidence I have found. This does 
seem to give a probable link between the variations in solar radiation 
and the dimensions of the Martian snows, and, as I have noted, seems 
to show that the Martian winters are more rigorous when solar activity 
is at a low ebb. 18 An analogous coincidence was found, to a lesser 
degree, for the southern cap in 1924. 13 According to my results, the 
differences in the intensity of radiation between solar maximum and 
minimum make up a very small percentage of the total — a conclusion 
which agrees with the ideas of Mr. Abbot, the distinguished secretary 
of the Smithsonian Institution in Washington. 

The Apparent Dark Band Surrounding the Polar Caps 

A dark zone is often seen round the melting snows of Mars. Lowell 
and W, H. Pickering, among others, have attributed it to water pro- 
duced by the melting of the polar snows ; they believe that this water 
is used by the Martians to irrigate their arid world, that the inhabitants 
of the planet transport the precious liquid to the temperate and equa- 
torial regions of the planet, that for this purpose their highly advanced 
science has created canals up to 5,000 kilometres long, and that what 
we see is not the true canal, but a belt of vegetation to either side of it 
— strictly curved or rectilinear. But as the dark band which is the basis 
of this conjecture is an optical effect, the chain of argument above does 
not convince many people. The illusory character of the band was 
first recognised by Schaeberle. 1 * I have confirmed this point of view 
by noting that the band, due to a contrast effect, does not obey the 
laws of perspective, and that it cannot be photographed. 18 



50 



References 

i Flammarion, La plane te Mart, vol I, pp 61-2. 

a Ibid, vol I, pp 40-2. 

3 Ibid, vol I, p 305, fig 176, and p 337, fig 193. 

4 Ibid, vol I, pp 58-9. 

5 Astronomic populaire, vol IV, p 132. 

6 See also my Mars Report for 191 1-12, in Mem BAA, vol 20, IV, p 170. 

7 Astronomie populaire, vol IV, p 135. 

8 Memoria, V, p 24. 

9 Sec also my note in Bull Soc Astr de France, vol 38, p 152, 1924. and also the 4th 
chapter of the second part of this work. 

10 See my Mars Report for 1911-12 in Mem BAA, vol 20, IV, p 171, 1916, where I 
noted this essential fact, Brett attributed the Martian caps to clouds, an idea 
refuted by Flammarion (La planite Mars, vol II, 285-6). In 1925 W. H. Wright 
revived Brett's idea, without mentioning him (Lick Obs Bull, no 366). I have 
objected to the idea because the lakes and crevasses of the Martian surface always 
keep to the same positions, which proves that they are surface phenomena (Bull 
Astr Soc de France, vol 40, p 139, 1926). Wright has admitted this, without 
acknowledgement to the author (Lick Obs Bull, no 389), 

1 1 Bull Soc Astr de Russce, vol 18, p 2436", 1912. I have never seen this work, which 
is not available in French scientific libraries. 

la Bull Soc Astr de France, vol 38, p 299, 1924. 

13 See roy note in Compt Rend de I' Acad des Sciences, vol 179, p 557, 1924. 

14 Publ Astr Soc Pacific, vol 4, pp 196-8, 1892. 

15 Astronomische Nachrichten, no 43 5 8, 1909, and 4472, 191 1. 



51 



The Atmosphere of Mars ; 
It's Clouds and Winds 



The Aerial Envelope of the Planet 

The existence of an atmosphere around Mars has been proved, 
since Herschel's time, by the formation and dissolution of the polar 
caps, establishing the condensation and solidification of water vapour, 
and its liquefaction and evaporation. This atmosphere is extremely 
transparent; its power of diffusing light is so feeble that it remains 
invisible over the bright part of the planet, and an observer on Mars 
ought to be able to see stars in full daylight. 1 The reason why we can- 
not see the dark patches up to the edge of the disk is because of con- 
trast, which augments the brilliance of the limb against the dark sky. 
Contrary to current opinions, I have nevertheless noted that the edge 
of the disk is in reality less luminous than the centre.* The Martian 
gravity is weak, and this is a further factor in the tenuity of the 
atmosphere. The weight of the Earth's atmosphere is reduced by half 
for every 5,000 metres of ascent, but to give the same effect on Mars 
the increase in height must be 14,000 metres. 

In 1 84 1 Maedler observed a blue tint on the terminator, 3 noted also 
by Molesworth in 1903.* It is difficult to attribute this to the blueness 
of the Martian sky, projected on to the deep black of that part of the 
planet which is not illuminated by the Sun. 

Atmospheric Veils 

The air of the planet, though much more rarefied than ours, is still 
dense enough for clouds to exist at a considerable altitude, indicating a 
troposphere comparable in height with that of the Earth. These clouds 

52 






are of three different kinds: yellow, blue, or invisible to the eye but 
showing up in violet and ultraviolet light. 

Yellow Clouds 

The idea of atmospheric veils having the same colour as Mars was 
first suggested by the French astronomer Honore Flaugergues in 
1809. 5 It was again proposed independently by Burton, of Ireland, in 
!g8 — a very distinguished observer who referred to orange clouds;* 
and finally by Douglass, who mentioned yellow dust in 1899. 7 I con- 




Fig 9 Vast yellow cloud, masking the Trivtum Charontis and 
neighbouring regions from 23-27 August 1929. (p m -2i6 reflector) 



53 



firmed this definitely in 1909 by direct observation of the Martian 
continents (Fig g), 8 as I found that these more or less transparent 
yellow or reddish veils — less red than the continents, incidentally — 
were very frequent; even more so than the white clouds.* I found 
moreover that they were most often seen near perihelion, when the 
solar heat, half as great again as at aphelion, produced stronger winds, 
so that the yellow particles and the lighter sand and dust would be 
more easily picked up from the Martian deserts. 10 During the opposi- 
tion of 1 924, the Meudon refractor showed that the rose or red colour 
was yellowed near the edge of the disk. In 1858, Father Secchi noted 
that the diminution of the red colour of Mars coincided with the fading 
of the bluish patches, 18 which was a noteworthy discovery, later con- 
firmed by Muggins. These yellow masses vary somewhat in thickness 
and in colour, which ranges from whitish cream to orange ; u they give 
to the rosy continents or to the islands a tint which may be orange, 
yellow or even citron; and as Burton found, 13 they can also make the 
polar caps look yellow at times. At Meudon, I have seen that since they 
are transparent, they sometimes give a very pale but luminous greenish 
tint to the already green areas of Mars. Moreover, with the o m '83 
refractor I have observed that they can sometimes cover extended 
areas for a long time ; this happened in 1 9 1 1 with the Mare Erythraeum 
(Fig 10). 14 On the other hand, rapid changes can sometimes be seen. 
At the perihelic oppositions of 1877, 1892, 1909 and 1924, they en- 
hanced the yellow colouration of Mars, sometimes greatly enfeebling 
or even concealing the dark areas for weeks on end. The most remark- 
able of all these clouds was that of the summer of 1909, carefully and 
skilfully studied during June of that year by our industrious colleague 
Monsieur G. Fournier, who had observed the planet with success for 
thirty years. I was able to follow the phenomenon at the Flammarion 
Observatory at Juvisy during August, when, on the 12th of that 
month, Mars was citron yellow, and it was nearly impossible to see 
patches normally as dark as the Mare Tyrrhenum, Syrtis Major and the 
Sinus Sabaeus! It was truly a unique spectacle. On the following days 
Mare Ctmmerium began to be lightly obscured, and the yellow cloud 
again covered almost the whole of the planet, the effects being least 

54 






., b" y/\ 



>&*** d. D= ( .11 I / \ 

I JL 



-:.'•:■ 




Fig 10 Immense orange-yellow veil, observed on Mars from 
3-23 November 1911, {o m -83 refractor) 



near Solis Lacus and Aurorae Sinus. During August only the Mare 
Sirenum retained tts normal intensity. I communicated my observa- 
tions of this cloud to Schiaparelli, and I had a reply from him on 29 
August 1909 from Monticello (Como), in which he said, among other 
things: 'The actual pallor of the tints of Mars and the difficulty of 
seeing the surface details clearly has been noted before, and has been 
attributed to various causes. For the moment, we must be content to 
wait and follow with care the gradual changes which will certainly 
occur, as during a similar occasion in 1886." In 191 6 I concluded that 
these yellow clouds remained at a lower level than the white clouds; 16 
but the rule is not an absolute one. 

Monsieur Lyot, who is one of the most informed and skilful of our 
young astronomers, agrees with me, and has constructed a polarimeter 
giving the amount of polarised light to a fraction of 1/1,000, so that his 
instrument is ten times more sensitive than that of Savart. In using his 
equipment with the great Meudon refractor, he has proved that the 
polarisation of Mars varies similarly to that of the Moon when the 



55 



planet's atmosphere is transparent ; but when there are yellow clouds, 
as in December 1924 and January 1925, the polarisation diminishes 
considerably, to return to its normal ratio after these aerial veils have 
dispersed. He has thus found that polarisation provides a very sensitive 
method of detecting the presence of light yellow mists on Mars, parti- 
cularly when the planet is near quadrature. 

On 8 July 1924, Mars appeared a solid, rather disturbed ruby red, 
while the dark regions in the area of the Solis Lacus were pale. I have 
found no plausible explanation for this phenomenon, which also sur- 
prised Monsieur Grenat. A month later, on 10 August, the planet had 
again become covered with yellow clouds, and presented a cream 
colour similar to that of Jupiter. 

White Clouds 

Independently of these yellow veils, whitish clouds are also seen on 
Mars, possibly comparable with our fogs, mists or perhaps even cirrus. 
Above all they are observed when the planet is well away from peri- 
helion, as though the lower temperature favours condensation of the 
water vapour. Schiaparelli attributed it to the low altitude of the winter 
sun. 18 Indeed, since we know from the snowy caps of Mars that water 
exists in the solid state, it should also be present as vapour, from which 
droplets and needles of ice could well produce the whitish clouds. It is 
not likely that they are dust-clouds similar to those of the Sahara. 

These clouds, which are generally pale, were first observed by 
Father Secchi in 1 858 ; he believed that he had seen a sheet of cirrus 
over the Syrtis Major." Normally they give the aspect of light mist; 
but sometimes they can become very bright, and rival the brilliancy of 
the polar cap itself. This happened, among other occasions, in 1905, in 
the north polar regions. They often appear to be higher-up than the 
yellow clouds, and they show a marked preference for the continents 
and the smoky-red islands. Barnard has seen them dim the southern 
snows. 17 Elsewhere they are most frequently observed in the north 
polar zone, probably because of the cold continental desert conditions 
there ; mists were observed in these regions by various observers, in- 
cluding the Dutch astronomer Kaiser in 1864 and myself in 1896-7, 



56 




Fig 11 Complex white veil, made up of roughly circular masses over 

Libya on 11 October X911; during the following days it moved toward the 

south-east. The details of the rounded masses are not accurate, but give an 

idea of the general aspect. (o m -Sj refractor} 



1911 and 1926, when they sometimes totally veiled the Mare Acida- 
lium. These condensations appeared to be particularly well-developed 
between Martian heliocentric longitudes 40 to 90 — that is to say, at 
the end of the northern winter." Moreover, in 1911, using the great 
refractor, I saw a thick cloud resembling a white mat entirely effacing 
the Mare Tyrrhenum, half of Hesperia and the following part of the 
Mare Cimmerium (Fig 11). This was an extremely rare phenomenon. 
In 1896-7 Cerulli, with his excellent o ro -38 Cooke refractor, noted a 
granular structure in a comparable white mass covering Cydonia; 19 
and in 191 1 I saw a great patch on Libya, made up of disconnected 
white flakes — a sort of cirro-cumulus on a gigantic scale (Fig 11). 
Again, in 1924, with the o m -83 I saw a similar but paler phenomenon 
in Hellas. This tendency to cloudy condensation and large round 
masses is very remarkable. The fact already noted — that the white 
clouds form more often over the continental regions and the brick- 
coloured islands — seems to indicate that these areas are elevated 
plateaux, on which water vapour can condense more easily than else- 
where. In this case the brilliancy of the clouds will be some sort of 



57 



function of the altitudes/of the lands above which they form. 

Any rainfall from these clouds must be insignificant, but it is pos- 
sible that the Martian vegetation is very sensitive to it,* 

Lands which Whiten under Oblique Lighting 

When the whitish veils reach the edge of the disk, the visible light- 
rays naturally pass through a greater thickness of cloud, and the clouds 
themselves ought to show increased brightness. It is to this which I 
attribute the very inconsistent phenomenon first noted by Browning 
in 1873," that lands are sometimes whitened during the course of the 
Martian day when seen under oblique lighting. 

Thus all the more or less transparent whitish mists on Mars should 
appear even whiter when near the terminator than when on the central 
meridian — and brighter when at the edge of the disk than when on the 
terminator. 







Fig 12 Let M be the centre of Mars, ABC the equator, DFG the limit of 
the atmosphere (very exaggerated in height), MT the direction of the 
Earth, MS the projection of the direction of the Sun, and IN the projec- 
tion of a part of the terminator. A cloud N, made up of droplets and 
needles of scattered ice, diffusing the light, lies above the terminator, and 
we see the particles along a depth ab. When crossing the centre, at N', we 
see the droplets along the lesser depth a'b'. And at the limb, at N", we 
see them along the greater depth a'b*. We have thus the inequalities: 
ab> a'b'; and ab < a'b" 



According to Monsieur Lyot, the white veils, unlike the yellow 
clouds, show more marked polarisation when near the edge of the disk 
than when near the centre. 

We cannot attribute these occasional whitenings to white frost at the 
edge of the disk. Our distinguished friend and colleague Monsieur 
Entile Touchet has shown that it is impossible for such frost to form 
in the full afternoon. 

Invisible Clouds 

Photographs taken in violet or ultraviolet light often reveal the 
presence of bright veils, invisible to the eye. 

The Wind of Mars, and its Velocity 

As on Earth, the Sun is naturally the main cause of all movement on 
Mars. Displacements of the white cloudy masses give us some idea of 
the velocity of the winds on our neighbour world. In 1896-7 Lowell 
and Douglass, from studies of the atmospheric veils, deduced speeds 
of 3okm/h." A brilliant patch observed in 1873 on Aeria by Burton and 
Lohse 88 led to a west-wind speed of 2skm/h: that is to say, 7 metres per 
second. Two white cloud masses which I saw from Meudon in 1911, 
near latitude 70 S, gave speeds between 29 and 36km/h, or 8 to 10 
metres per second. Finally, in 1924 I measured the velocities of Mar- 
tian winds at between 14 and 3ikm/h, that is to say 4 to 7 metres per 
second. These velocities approach those of our depressions, but the 
rarefaction of the Martian atmosphere favours high wind-speeds in 
spite of the lesser amount of heat received from the Sun. Moreover, on 
Mars there are no doubt stronger local circulating winds which we 
cannot observe. But,, as Maunder has predicted on theoretical 
grounds, 8 * we have not yet observed on Mars the 'light breezes', 
'fresh breezes', 'strong breezes' and 'fresh winds' of the Beaufort 
scale. 

Turning and Reversing South and West Winds on Mars 

In 1896-7, Lowell and Douglass detected a south wind blowing in 
the southern hemisphere of the planet." In ign, with the o m -83 



58 



59 



refractor, I saw a reversing strong westerly air-current (Fig 13) in high 




Fig IS Winds observed on Mars. i:from 11 to 14 October 1911. 2: 13 
and 14 November 19x1. 3: from 10 to 13 October 1924. 4: movement of a 
cloud according to descriptions by Burton and Lohse on 24 and 25 May 

1873 

latitudes, just as on the Earth. In 1924, also at Meudon, I noted a 
gyratory movement of the Martian clouds in an effectively anti- 
clockwise direction at latitude 30° N, just as in our own temperate 
regions (Fig 16). 

Cloudy Projections on the Terminator 

The temporary white or yellow projections seen along the ter- 
minator of Mars are not always produced at the same points on the 







Fig 14 A: Oct 10, at xoh om. B: Oct 11, igh 40m. C: Oct is, 21k 

1 2m. Cloudy projections on the Martian terminator, observed in October 

1024, (o m S3 refractor) 



60 



surface. They must therefore be due not to mountains, but to clouds. 
Keeler in 1890, Douglass in 1909, van Biesbroeck in 1924, and myself 
in 1929 have all seen them completely detached from the terminator. 
In 1896-7 Lowell and Douglass derived heights of between 13 and 
24km. ae In 191 1, from Meudon, I noted a phenomenon over Icaria 
which apparently rose to 7km. In 1924, with Monsieur Baldet, I 




Fig 15 Movements of two cloudy masses above Hellas and Yaonis Regio 
on 10, 11, 12 and 13 October 1924. (o'"Sj refractor) 

observed a great double protuberance, yellowish-white in colour 
(Fig 14) above Hellas and Yaonis Regio; it was also seen by Monsieur 
Deslandres. According to my calculations, its summit was between 8 
and 20km above ground level. Fig 15 shows the extent of this feature, 
which was 3,000km long, and also the movements and points of cul- 
mination of the centre of the two main bright masses of which it was 
composed. The great apparent height of the Martian clouds seems to 
establish that, as we have already said, the troposphere is as high as 
ours; and this conclusion, drawn from observation, agrees with theo- 
retical calculations based upon gravity. Moreover, on 16 March 1929 
I observed an immense dark yellow projection over Zephyria, com- 
pletely detached from the terminator. 

Monsieur Lyot has justifiably noted that the altitudes deduced for 
these cloudy projections are too great, because of the invisibility of the 
true theoretical terminator, which is obliquely illuminated by the rays 
of the Sun. 

Monsieur Baldet noted an ephemeral blackish streak accompanying 
the projection of 10 October 1924, but he could not explain it. I have 

61 






a5o 360 D70 280 390 3oo 3io 3ao 33o 34o 3So 







-20 jM^sdn" 







a8o 



ago 



3oo 




-3° 



e.M.A 



1000 

1 



aooo 

I 



3ooo 



km 



2^ 16 Chart showing the movement of the central point of the elouay 
masses observed as projections on the terminator of Mars from IO-13 
October 1024. (o m -S3 refractor.) Continuous lines indicate the trajectory 
of the apparently highest point; dashed lines indicate the centre of the 

two clouds 

confirmed this object, and believe it to be due to the shadows of bright 
clouds under very oblique illumination by the rising Sun, and lasting 
for only a few minutes. An analogous streak is shown in Fig 14C. 




Fig 1 7 Here is a simple graphical method, which I gave several years ago for 
the use of amateurs in finding the apparent height of a protuberance above the 
surface of Mars (2): 

Let C be the centre of the planet, LTO a part of its dark hemisphere turned 
toward the observer, TMRNO the terminator, OL the greatest defect of 
illumination, MPN the protuberance drawn as observed (exaggerated in sise 
here, for the sake of clarity), andRP, parallel to CO, the maximum projection 
of the object. 

Imagine next that this segment of the Martian globe has turned downward by 
oo", around COL, which is assumed to be the axis. Then T coincides in projec- 
tion with C, and O falls on O'. Join O to C, and CO' will be the projected 
terminator. MEN, the base of the protuberance, will fall on M'R'N'; and as the 
Sun's rays are normal to the plane of the terminator, P will be projected atP', 
on R'P', perpendicular to CO'. 

From the point O', draw the tangent O'A = R'P', and join A to C. B is 
now the point where the secant AC cuts the surface of the sphere; and AB is the 
true height, h, of tlte protuberance above the surface of Mars on the scale adopted 
for the drawing. 

But: k = sec O'B—i; 

or h = 1 — 1. 

cos O'B 

A protractor will give the value of O'B. 

The radius of Mars is 3,363km; and a table of natural cosines will enable 
the height of the protuberance to be determined without difficulty. 



References 

1 I announced this theory with Flammarion in Butt Soc Astr de France, vol 13, Sept 
1899, and vol 38, p 50, 1984. 

2 Month Not RAS, vol 71, p 32, 191 1. 



62 



3 Astr Nach, vol 19, 1842, col 19. 

4 See my Mars Report for 1903, Mem BAA, vol 16, IV, p 60, 1910. 

5 Flammarion, La plane te Mars, vol I, p 87. 

6 Sci Trans Roy Dublin Soc, vol I, new series, p 156. 

7 Flammarion, La planite Mart, vol II, p 476. 

8 Bull Soc Astr France, vol 13, P 44°, »9°9 i Astr Nach, no 4354. io°9- 

9 See my Mars Report for 1905, Mem BAA, vol 17, II, p 37, 1910. 



63 



io Bull Soc Astr France, vol 38, p 54, 1924; see also my Mars Report for 1909, in 

Mem BAA, vol zo, II, p 37, 1915. 
11 Mcmorie dell'Osservatorio del Collegia romano, no 3, p 18, 1859. 
1% See my note in Month Not RAS, vol 76, p 414, 1916. 

13 Sci Trans Roy Dublin Sac, vol 1, 1880, new series, p 169. 

14 See my Mars Report for ign-ra, Mem BAA, vol 20, IV, pp 133-4, 1916. 

15 Ibid, p 123. In 1927, W. H. Wright, without quoting me, repeated the view that 
the yellow clouds are at a relative low altitudely (Lick Qbs Bull, no 389). 

16 Memoria, V, p zq. 

17 Op cit, p 19. 

18 Astrophysical Jnl, vol 17, p 254, 1903. 

19 TrfJmpter referred to W. H. Wright's idea that the north polar cap of 1926 was 
an atmospheric phenomenon (Jnl Astr Sac Pacific, vol 39, p j 05, 1927). Yet I had 
not only observed and published my opinions, but had also predicted the effect a 
year earlier (Butt Astr Soc France, vol 40, pp 279 and 511, 1926). 

20 I examined this idea of rain fertilisation in Bull Soc Astr France, vol 38, p 52, 1924. 

21 Webb, Celestial Objects for Common Telescopes, 1881 ed, p 149. 

22 Flarnmarion, La planete Mars, vol II, p 301. 
»3 Ibid, vol II, pp 2ii and 227, Figs 134 and 146. 
34 Are the Planets Inkabiteds p 76. 

25 Flarnmarion, op cit, vol II, p 301. 

26 Flarnmarion, op cit, vol II, p 301. 

27 Bull Astr Soc France, vol 28, pp 439 and 460, 1934. Fifteen years after my publica- 
tion from Meudon, W. H. Pickering, without citing me, announced the same 
phenomenon and gave the same shadow explanation for it (Popular Astronomy, 
vol 34, p 157, 1926). 

A simple graphical method (Fig 17) for deducing the height of a projection from the 
Martian limb is given in the Mars Report for 1911-12, Mem BAA, vol ao, IV, p iaa, 
1916. 



64 



8 

Physical Conditions 
and Habitability 



Martian Ctimatology 

The presence of snow at the poles proves that the Martian surface, 
like that of the Earth, receives so little heat from the interior that if 
this were the sole source of warmth, the temperature could never rise 
as high as o° C. Some theoretical calculations, based on the square of 
the distance from the Sun, have led Newcomb to suggest that Mars is 
a frozen globe. The idea is not new. However, it is not supported by 
the fact that the polar snows melt, and that this melting takes place 
before our eyes. Another objection is to be found in the fact that the 
ice is only seen round the poles. Its absence from the equatorial re- 
gions tends to prove that there, as on Earth, the temperature is too 
high for it to appear or persist. As we have noted, the Martian snow 
forms only during the long polar night. Moreover, the idea of a frozen 
Mars cannot explain the enormous changes observed on the surface. 
Poynting, taking into account the square of the distance together with 
Stefan's Law, has found — 28 for the mean temperature of the planet, 
—20° for the equator. 1 Moulton has admitted that in the equatorial 
regions the temperature can exceed o° C. a As John Phillips supposed 
in 1865, it seems that the very transparent atmosphere of Mars ought 
to be transparent to the visible rays of the Sun and opaque to the in- 
visible heat reflected from the surface; 3 this is confirmed by the 
yellow clouds which often hide the dark regions after perihelion* and 
by the brown discolouration of the dark areas produced at very 
different times. It has been justifiably claimed that on Mars the nights 



65 



are very cold. Finally, the absence of extensive liquid surfaces which 
would be subject to evaporation, together with the rarity of massive 
white clouds and the failure of Campbell, from Mount Whitney {the 
highest point in the United States) to detect water vapour in the 
Martian atmosphere by spectroscopic methods, 8 indicate a very 
marked dryness of the atmosphere. The climate of the whole globe is 
more or less desert-like, and Mars has reached a stage of advanced 
decrepitude. 

From the kinetic theory of gases, Johnstone Stoney has concluded 
that all molecules moving at a velocity of 4,803 metres per second or 
greater wiU have escaped from Mars. This is correct. However, he 
then adds that the atmosphere cannot contain water ; that without 
water, there can be no vegetation analogous to our own ; that without 
vegetation, there can be no free oxygen ; and that the Martian atmos- 
phere is probably composed of nitrogen, argon and carbon dioxide, all 
of which are heavy gases. 8 Everybody will admit that these conclusions 
are interesting, but unfortunately I must reject them. I do so because 
of my observations of the colour-changes in the green areas, which 
turn brown in summer exactly as do the leaves of our trees. Also, 
Johnstone Stoney will accept only clouds made up of carbon dioxide, 
but I have found that the whitish clouds are at a considerable altitude 
above the ground. As so often in the study of Nature, we have a set 
of facts which may be incomplete, but which can at least lead us on to 
some logical deductions. 

However, it is only right to add that my observations of Mercury 
and the satellites of Jupiter tend to confirm the very ingenious ideas of 
the Irish astrophysicist with regard to these small worlds of the Solar 
System — all of which are characterised by the lack or paucity of 
atmosphere. 

The Question of Life on the Planet 

The doctrine of the plurality of worlds dates back to Orpheus, who 
lived fourteen centuries before Christ f and in ancient times the genius 
of Thales of Miletus recognised that the other worlds in the universe are 
made up of the same elements that we know on Earth 8 — a conclusion 



66 






whose accuracy was proved speetroseopically by the discoveries of 
Kirchhoff in the nineteenth century. 

We have seen that the great extended dark areas of Mars behave as 
though covered with vegetation, which makes it very probable that one 
form of life exists there. But by the side of flora, we often meet with 
fauna. This is an argument which many people have used when dis- 
cussing Mars. Also, the melting of the polar snows and the absence of 
ice in the temperate and equatorial regions proves that the temperature 
is not too low to support living things, since animals well known to 
Man exist quite well in the cold of up to — 72 in Eastern Siberia. 
Moreover, the observations of clouds at considerable heights shows 
that though the atmosphere of Mars is very thin, it is still able to hold 
ice-needles or water-droplets in suspension — or even particles of dust. 
Therefore, the atmosphere does not seem to be too rarefied for living 
things such as vegetation.* In this connection, we must bear in mind 
that the people of Tibet have no difficulty in breathing in an atmos- 
phere twice as rarefied as ours. If, then, we consider also life's mar- 
vellous power of adaptation, one of the aims of the Creator of the 
Universe, we can see that the presence of animals or even human 
beings on Mars is far from improbable. This was the view held by 
Fiammarion, Schiaparelli, Moulton 10 and others. However, it seems 
that advanced life must have been confined to the past, when there was 
more water on Mars than there is now; today we can expect nothing 
more than vegetation around the vast red wildernesses of the planet. 

The Sky from Mars 

The thinness of the atmosphere, and the greater distance of Mars 
from the Sun, means that the Martian sky must be a very dark blue, so 
that — as we have seen — brilliant stars are visible in full daylight. The 
glow at dusk and dawn must be very feeble and brief. Also, refraction 
and scintillation there ought to be less than it is here, and it is the 
same with optical and electrical phenomena such as our polar aurorae. 
Winds are feeble, whitish clouds inconsistent and transparent ; but on 
the other hand there will be more yellow clouds than are found above 
terrestrial deserts. 



67 



Seen from this neighbour world, the constellations and the Milky 
Way would be a little more brilliant than from Earth, Jupiter would be 
splendid, and the Earth and Venus, always morning or evening stars, 
would appear when rising or setting as magnificent stars of the first 
magnitude. Saturn would appear more brilliant than it does to us, 
Mercury fainter; Uranus would be easily visible with the naked eye, 
and so too would many asteroids. Naturally, comets would be less well 
seen than from Earth ; and great cometary spectacles such as those of 
1843 and 1959, 1 86 1 and 1882 would be absolutely unknown. 

The Sun, reduced to a mean diameter of 21', would be too small for 
any but the largest spots to be seen with the naked eye ; and on occa- 
sions the round, black disks of the two tiny satellites would be pro- 
jected against it. Finally, the charm and special character of the Mar- 
tian nights would be enhanced by the very rapid retrograde march of 
the premier moon, Phobos, with the excessive slowness of the second 
moon, together with the changing phases and frequent eclipses of 
these two miniature worlds. 



References 



Radiation in the Solar System: its Effects on Temperature, in Phil Tram Roy Soe, 
vol 202. The precise determination of planetary temperatures is carried out by 
using the thermocouple. The formulae, first worked out to satisfy the results of 
visual observations of Mars, have given —140° centigrade for Jupiter! This result 
is naturally impossible; I have shown that the Jovian phenomena have no re- 
lationship with the Sun, but are intrinsic to the planet (Compt Rendut de I' Acad 
Set, vol 183, pp 1089-90, 1920). The fact that Jupiter does not rotate as a solid 
body, as is shown by the general nature of the details and the very great intrinsic 
activity, are phenomena equally characteristic of the Sun, but not of a cold world 
such as Mars. They can be explained only by a high temperature. For Mercury, 
the thermocouple has given results of from 227° to 417° C at Mount Wilson, from 
75 to ioo° C at Flagstaff. It is difficult to give a more decisive proof of the un- 
reliability of temperature estimation than by quoting an error of hundreds of 
degrees centigrade for a single object. 
An Introduction to Astronomy, New York, p 283, 1 916. 
Proceedings of the Royal Society , vol 14, p 45, 1865. 

In 1877 it was observed between 320 and 333° heliocentric longitude; in 1909 
from 300° to 338°; in 1924-5, from 40 to 6o°. 

The Spectrum of Mars as observed by the Crocker Expedition to Mount Whitney, 
in Lick Obs Bull, No 69. 



6 Sci Trans Roy Dublin Soc, vol 6, new series, pp 321-2, November 1897. 

7 Proclua Diadochus, Commentary on Plato's Timon, III, 154A. 

8 Achille Tatius, Introduction to the Phenomena of Aratus, 11 ; Stobee, Physique, I, 
24, etc. 

9 Mr J. C. Duncan, to whom we owe a beautiful demonstration of the existence of 
dark nebulous masses in the universe, finds — with justification — that the air of 
Mare is unwholesome, but that this impression is weakened by the existence there 
of vegetation (Astronomy, p 244). 

io Op cit, p 287. 






68 



69 



The Two Satellites of Mars 



Discovery of the Satellites 

The two minute companions of the planet, which are so curious and 
interesting and whose diameters are comparable with that of Paris, 
were, as everyone knows, discovered in 1877 by Asaph Hall at the 
Observatory of Washington — thanks to the perseverance of his wifel 
The more distant of these little worlds was found by the American 




Fig 18 The world of Mars, attended by it% two satellites Phobos and 
Deimos, observed on 23 September 1000 at 22.40. (o m -S3 Meudon 

refractor) 



70 



astronomer on 1 1 August 1877, and the closer-in on 17 August. Hall, 
with justification, gave them Homeric names: Phobos (Terror) to the 
inner, Deimos (Fear) to the outer. He declared that he had been in- 
spired by two lines of the immortal poet, relating to Mars: 1 

He ordered Terror and Fear to harness his steeds ; 
And himself donned his shining armour. 1 

Elements 

The numerical data relating to the two satellites are as follows: 

Phobos Deimos 

Distance, in radii of die planet 2-77 6-95 

*7°-5 a7°-5 



Orbital inclination to the orbit of Mars 



Sidereal period 



7h 39m I3'98 3°h 17m 54*91 



The gravitational pull of the equatorial bulge of Mars leads to an 
advance of the major axis arid a regression of the nodes in the orbit of 
each satellite. The full cycle is z\ years for Phobos and 56 years for 
Deimos, 

State and Nature of the Surfaces of the Satellites 

Phobos is of the 12th magnitude — brighter than Deimos, which is 
only of the 13th; probably it has also a greater volume, but it is more 
difficult to see, because it is closer to Mars and is often concealed by 
the brightness of the planet. In 1909, using the great refractor together 
with Monsieur Idrac, I saw the satellites more than once (Fig 18) 5 and 
as Phobos appeared white and Deimos bluish, they must have surfaces 
which are radically different from that of the red world around which 
they turn. Their nature appears to be similar to those of the asteroids. 

Remarkable Phenomena presented by these Little Worlds 

We will now review the quaint peculiarities of these two asteroid- 
like worlds. 

The diameter of Phobos seems to be about 12km, and that of 
Deimos 10, according to photometric data given by E. C. Pickering. 
Phobos effectively completes three revolutions round Mars in a day, 
and its 'month' is thus less than 8 hours — three times shorter than the 
planet's day. 



71 






Ledger has noted that the rapid movements of Phobos among the 
stars will permit Martian navigators to determine longitudes by lunar 
distances with much greater precision than is possible on Earth; but 
the absence of seas on Mars makes this method useless. 

To an observer on Mars, Phobos will always rise in the west and set 
in the east, a case unique in the Solar System. However, in this connec- 
tion C. T. Whitmell has noted that the particles making up Saturn's 
ring system also revolve more quickly than the primary planet spins.* 

It has been calculated that for certain points on the equator of 
Mars, Phobos, moving very quickly, will remain above the horizon for 
only 4^ hours/ and that it will rise at mean intervals of r i h 7m. On the 
other hand the excessively slow movement of Deimos, from east to 
west, will make it remain above the horizon for about 60 hours, that is 
to say five times as long as with our Moon, 3 and the mean interval 
between successive risings will be 132 hours. 

Seen from Mars, Phobos subtends an apparent diameter of 7', and 
will be twice as large, in surface area, when at the zenith than when at 
the horizon ;* Deimos subtends 2^', and is three times as large when at 
the zenith as when at the horizon. 6 It follows that the total light re- 
ceived on Mars from these two miniature worlds is only a feeble frac- 
tion of that of our Moon, particularly as the Sun sends them only 43 
per cent of our own light. According to C. A. Young, Phobos shines in 
the Martian sky about as brilliantly as Venus does to us. Moreover, 
from the planet, neither satellite — particularly Phobos — can be seen 
absolutely full. 8 

As Phobos goes through all its phases in 7$ hours, it goes through 
about five-ninths of these phases while it remains above the horizon as 
seen from the equator. 7 During the 24b 37m Martian day, Phobos may 
perhaps be full, then new, full and new again before setting. 8 And as 
Deimos goes through its phases in 30^ hours, it will go through them 
almost twice while it remains visible as seen from the Martian equa- 
tor. 9 During a Martian day or night, Deimos passes through two-fifths 
of its phases, or more than four-fifths of them during the complete 
24-hour day of the planet. 10 

Phobos often eclipses Deimos, and is itself frequently eclipsed, 

72 



because on average it appears full once in every three oppositions. 11 
For about one-sixth of the Martian year, near the end of the Solstices, 
there will be a succession of full moons, and during one-third of the 
year, near each of the equinoxes, there will be a succession of eclipses ; 
some 665 eclipses near each equinox, or 1,330 during the planet's 
year. 12 The eclipses of Deimos are less frequent than those of Phobos 
— about 130 in each Martian year; and on average there are four full 
moons in five oppositions. 13 When one of the satellites is eclipsed, it 
can receive no light from the other, even if the latter is neither eclipsed 
nor occulted by Mars. If both satellites are eclipsed at the same time, 
or if one is eclipsed and the other occulted by the planet as seen from 
the other satellite, the satellite within the shadow of Mars must remain 
invisible — and the presence of the eclipsed satellite will be betrayed 
only because it occults the stars behind it ! 

Near the equinoxes, the satellites often pass in front of the Sun, 
showing up as black circles. Phobos can cover one-third of the solar 
diameter, Deimos nearly one-ninth. Phobos passes in front of the Sun 
almost 1 ,400 times in a Martian year, and the duration of the transit is 
only 19 seconds for the centre of the satellite; Deimos transits 130 
times a Martian year, the duration of each transit being 108 seconds. 1 * 
On rare occasions, both the little moons may pass across the Sun's disk 
at the same time. 

The satellites remain permanently hidden from a wide zone around 
each pole of Mars. Thus Phobos cannot be seen from a cap 41 ° in 
diameter centred on each pole; Deimos one of 15 . 

Note, finally, that they can produce no tides upon a world on which 
there are no seas. 

The Rotation of the Satellites 

As Deimos has been observed from Harvard to be brighter when to 
the east of Mars than when to the west, 16 it seems that each little 
satellite must always keep the same face turned toward its primary. 

This follows on the fact that Iapetus, the eighth satellite of Saturn, 
has a rotation period equal to its period of revolution, and that the 
Solar System presents other examples of the same kind. In effect, the 



73 



rotation of the Moon round the Earth is analogous to that of Iapetus 
round Saturn ; and the patches which I have observed on the 1st and 
Illrd satellites of Jupiter indicate that they behave in the same way. 18 
Then, too, my confirmation of the 88-day rotation of Mercury, 1 ' first 
noted by Schiaparelli, is additional support. 

Now, if Saturn, with its low density of 0-7 (water = 1) acted upon 
Iapetus when the satellite was in a plastic state, and produced tides 
which have made Iapetus lose its independence of rotation despite its 
great distance of 62 mean Saturnian radii, the other satellites of Saturn 
and those of other planets whose distances are less, both relatively and 
absolutely, than that of Iapetus from Saturn, must also have captured 
rotations. They will have suffered more energetic tidal braking from 
denser primaries, 18 It follows that the two satellites of Mars, the four 
large satellites of Jupiter and the fifth discovered by Barnard, the seven 
others of Saturn, the four of Uranus and that of Neptune ought always, 
apart from librations, to present the same faces to their respective 
primaries. If the tidal forces vary according to the inverse cube of the 
distance, the braking power on rotation varies according to the sixth 
power of the distance; and this means that if, for example, Iapetus 
were at half, one- quarter or one -eighth of its actual distance, the tides 
caused by Saturn would have a braking action which would be respec- 
tively 64, 4,096 and 262, 144 times more powerful. Thus all the above- 
mentioned satellites have been subjected to tidal action which is 
absolutely enormous compared with that on Iapetus — and their rota- 
tions have been very efficiently captured. 

However, the fact that the Earth has kept its independent rotation, at 
216 solar radii, shows that the Vlth, VHth, VIHth and IXth satellites 
of Jupiter and the IXth satellite of Saturn are too distant from their 
primaries to have revolution periods and rotation periods of equal 
length. 

Sir George Darwin has concluded that 'the ultimate destiny of 
Phobos seems to be absorption into the planet'. 18 

Mars Seen from Deimos 

Observed from this little' world, the planet would subtend 16 , 



74 



having thus an apparent diameter 32 times greater than that of the 
Moon as seen from Earth. Mars would seem to turn on its axis from 
west to east in 132 hours. Phobos would 80 present all its phases, passing 
sometimes in front of the disk of Mars and at other times being 
occulted by it. At these passages Phobos and the planet would present 
essentially the same phase; the satellite would therefore pass across 
Mars at full phase, gibbous, half or crescent, with the planet presenting 
at the same time a corresponding phase of full, gibbous, half or 
crescent. 

Mars Seen from Phobos 

The spectacle of Mars seen from the inner satellite would be incom- 
parable. The immense nearby globe of the planet, only 6,000km away, 
would appear truly gigantic, subtending a diameter of 42 , or 82 times 
that of the Moon, and extending more than half-way from the horizon 
to the zenith! Mars would seem to turn on its axis in nh 6m, from 
east to west,* 1 in a sense opposite to its true direction of rotation ; thus 
with south at the top, Mare Sirenum, for example, would drift to the 
right instead of advancing to the left. Moreover, the close proximity 
would mean that instead of seeing 180° of the Martian globe, only 137 
would be on view; moreover the patches at the centre of the disk 
would appear greatly enlarged, by perspective. True, an astronomer on 
Phobos would see no canals; but he would marvel at the contemplation 
of myriads and myriads of irregular patches with colourations so strong 
and so varied that no artist could possibly give a faithful rendering of 
them. 



References 

1 Homer, Iliad, XV, 1 19-20. 

s The Moons of Mars, p 3. 

3 Proctor, Old and New Astronomy, p 550. 

4 Ibid, p 550, 

5 Whitmell, The Moons of Mars, p 5. 

6 Ibid, p 10. 

7 Ibid, p 3. 



75 



8 Ibid, p 4. 

9 Ibid, p 8. 

10 Ibid, p 9, 

1 1 Ibid, p 4. 

12 Ibid, p 4. 

13 Ibid, p 9. 

14 Ibid, pp 5 and 9. 

15 Annals of Harvard College Observatory, vol XI, part II. 

16 Comptes Rendus de I'Aead des Sri, vol 185, pp 639-40, 1927; Bull Soc Astr France, 
vol 42, pp 130-2, 1928. 

17 Comptes Rendus de I' Acad des Set, vol 185, pp 756-8, 1927 ; Bull Soc Astr France, 
vol 42, pp 1-16, 1928. 

18 Bull Soc Astr France, vol 42, p 133, 19*8; Jnl BAA, vol 39, pp 87 and 221-2, 
1929. 

19 The Tides and Kindred Phenomena of the Solar System, p 268, 190 1 , 

20 Whitmell, op cit, p 10. 

21 Ibid, p 6. 



FART 2 

TOPOGRAPHY OF MARS 



76 



Introduction 






The maps at the end of this memoir, which may be said to represent 
a mean state of the surface of Mars — though some areas are very 
changeable — are based on all my observations with the o m -83 Meudon 
refractor since 1909; on those which I made earlier with less powerful 
instruments from 1888;* and on the beautiful drawings by Millochau, 
my predecessor at the great refractor, in company with my learned 
colleague M. V. Burson. The photographs of Mars taken by Lamp- 
land, Lowell, Barnard, Hale, Le Morvan,f Quemsset, Hubble and 
Danjon have been observed carefully during my researches. First, Mr 
Lampland has obtained very beautiful photographs of Mars. His re- 

• I followed Mars for the first time in 1888 from the island of Prinkipo (Sea of 
Marmara) with an o m -c>75 refractor; in 1800 at Pera, Constantinople, with the same 
instrument; in 189a, again at Prinkipo, with an o m -io8 refractor; in 1804, at Paris, 
with an o m -to8 refractor; and at Juvisy with the o m -z4o equatorial at the Flammarion 
Observatory; in 1896-7 at Juvisy, with the o m '24o equatorial and an o m -io8 refractor; 
in 1898-9 at Juvisy, with an Q m -zs° objective fitted to the equatorial; in 1900-1, still 
at Juvisy, with an old o rai Z4o objective at the Observatory; in 1903, 1905 and 1907 at 
Paris with my o m -2l6 Calver reflector; in 1909, first at Juvisy with the o m -24 refractor 
and the o m '2i6 reflector, then with the great o m -83 Meudon refractor; in 1911-12, at 
Meudon, with the o m -83 refractor and the o""-ai6 reflector; in 19 13-14 and 1916, at 
Meudon, with the same reflector; in 1918, at La Frette (S. & O.) with the o m -32 Calver 
reflector belonging to my good friend Andre Barbier; in 1920 at Meudon, with my 
o m -ai6 reflector; in 1934-5, 1926-7 and 1928-9 at Meudon, with the o m -83 refractor. 
Finally, I observed Mars once, on 19 February 1929, at the Paris Observatory, together 
with M Giacobini, with the great o m -38 equatorial of the East Tower. 

t When I asked M Le Morvan if he had any photographs of Mars, the eminent 
photographer of the lunar surface took for me some beautiful photographs of the 
planet in violet light, using the great equatorial coudi at the Paris Observatory. It is, 
of course, well known that before obtaining his magnificent photographs of the Moon, 
M Le Morvan worked unceasingly for four years in order to meet the thermal require- 
ments of this instrument which we owe to Maurice Loewy. 

79 



suits since 1905 have been surpassed only by Barnard and Hale, 
operating with great apertures. But even the best photographs — those 
of Mr Hale, which are truly marvellous— are Far from showing the 
details which can be seen with the Meudon refractor. Photography is 
above all valuable in revealing feeble halftones, and it was thus that 
in 1924 M Quenisset, using an aperture of only o m -ii, was able to 
take photographs showing dark shadings which were visually observ- 
able only with great instruments. In addition, the admirable observa- 
tions of Schiaparelli are given in detail — because despite his single or 
double 'canals', which do not exist as rectilinear, geometrical bands 
on the planet, his work is of great creative importance. Where he has 
drawn a 'canal' not confirmed by a complex series of dark patches, the 
map shows the name given, along the direction of the line glimpsed. 

As well as the results of my observations, the descriptive text gives 
an analytical account of the areographical work undertaken since the 
time of Huygens. I have also used my correspondence with Schiaparelli, 
Barnard and Hale. 

Finally, there are places in which I mention certain results formerly 
obtained visually at Flagstaff. Lowell, whom I knew personally, was 
sincere; and Douglass has since made some good original observations. 
Also, when one or the other of these observers claims to have seen a 
lake during more than one opposition, or has noted a very clear colour 
on a dark patch, I have thought it right to mention the fact in my 
account of the observations. 

Thanks to the kindness of M Lamiable, Secretary of the Meudon 
Observatory, I have been able to consult the invaluable drawings of 
Trouvelot, and to copy them and reproduce them in my text. 

The following table gives the approximate positions of the principal 
points on the surface of Mars. The ordinary figures give the positions 
deduced from drawings; underlined figures, the measures or estimates 
made direct on the planet (naturally, corrected for phase). 

The last column of the tables gives the positions adopted on the 
maps accompanying this volume, positions which are sometimes a 
combination of my data with those of Schiaparelli in 1877-9; and * 
have also examined a beautiful series of positional measures made by 
M Ilario Sormano on the photographs taken by Lowell and Lampland 

80 









in 1907. Fastigium Aryn has been chosen as the zero point for areo- 
graphic longitudes. 

My observations of the transits of the dark patches across the central 
meridian in 1924 show that the data concerning Martian longitudes 
given in the American Ephemeris certainly need to be corrected by 
+3°- 

The historical account which follows gives the concise history of 
each point on the surface of the planet. The words continent, coast, 
bank, shore, beach, peninsula, cape, promontory, island, sea, Mediter- 
ranean, gulf, bay, port, estuary, outlet, sea-arm, channel, lake, tide, 
marsh, etc are given in a purely conventional way to simplify the 
terminology, 

I have respected the beautiful nomenclature of Schiaparelli, and 
wherever possible that of Lowell for certain lakes, giving the names in 
a form agreeing with the spirit of that of the Italian astronomer. 
Brackets following the name of a feature give the initial of the 
astronomer who has given the name, and the date: S = Schiaparelli, 
L = Lowell, C = Cerulli. The names which I have introduced are 
not followed by any initials; they have been drawn, like those of 
Schiaparelli, from the Bible and from the geography and mythology 
of Ancient Greece. 

This question of nomenclature is complicated, because euphonies 
have to be taken into account— and the ancient names should not be 
used without a deep knowledge of the Greek language. 

For greater convenience, I have arbitrarily divided the surface of 
Mars into five sections; the first three each extend across 120 of 
longitude, covering a belt right round Mars, going to 6o° of latitude 
to either side of the equator, while the two latter cover the glacial 
zones, to the poles from latitude 6o° N or S. 

Dimensions are sometimes given in degrees; one equatorial degree 
= 60km. 

Finally, the following abbreviations are found in the text: N = 
north, S = south, E - east, W - west; E denotes areographic east 
(west for the observer) and W denotes areographic west (east for the 
observer); w = the longitude of the centre of the disk, ^ = the latitude 
of the centre of the disk, and e = heliocentric longitude of Mars. 

81 






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Mare Tyrrheiuim, Syrtis Major 
and Sinus Sabaeus 



chersonesus (S, 1 877). This is a great blank peninsula of the 
southern temperate regions, of form and dimensions comparable 
with those of Indo-China. It prolongs the SW part of Ausonia. It is 
confused on the sketches of the first observers, but we find it well 




Fig 19 The reddish lands of Chersonesus and Ausonia Aus traits, on 14 
October 1924. (o m -S3 refractor) 

represented by Lockyer in 1862. Schiaparelli, using hiso m -2i8 refrac- 
tor in 1877 and 1879, saw it as a sort of slender horn. However, the 
observations I have made with the great o m -83 Meudon refractor 
since 1 909 show Chersonesus in the form of a bird's beak, going 
upward toward the SW and then bending down on Hellas (Fig 19); 
this strange topographical configuration has been amply confirmed by 
the beautiful photographs of Mars taken by Barnard with the i m '02 
Yerkes refractor, and by Hale with the i m -52 Mount Wilson reflector. 



86 



This land is 'smokier' than the continental regions, as was shown on 
the drawings made by the Dutch astronomer Kaiser as early as 1862, 
and on those of many other observers since. At Meudon, the colour 
appeared to me to be brick-red and coppery vermilion, sometimes 
particularly strong in 191 1. 

Like every point on the surface of Mars, Chersonesus appears orange 
or amber from time to time because of the interposition of yellow 
clouds in the planet's atmosphere; and this is what I often observed 
in 191 1. Moreover, Chersonesus sometimes appears whitish, as do 
other Martian lands, when it is near the edge of the disk — particularly 
when Mars is well away from perihelion. Thus on 23 December 1 864 
Kaiser found it almost as white as the polar snows; in 1879, Schiaparelli 
often observed it as very brilliant near the limb; in 1882, he once 
noted it as strongly white all over ; and the preceding coast seemed to 
be persistently covered with whiteness in 1 886. 

On 28 August 1896, Hussey observed in these latitudes a brilliant 
projection from the terminator. At this time he was using the o m '9i 
refractor at the Lick Observatory. 

ausonia (S, 1877). By this name Schiaparelli denoted an immense 
region extending from Promethei Sinus to Aeria, along almost a 
quarter of the circumference of Mars. It has been conveniently 
divided into two parts, Ausonia Australis and Ausonia Borealis. 

ausonia australis. The form of this diffuse and desolate land was 
first vaguely represented by Beer and Madler in 1830 with an 
o m io9 refractor. Lockyer showed it better in 1862; but the skill and 
observing methods of Dawes, and Proctor's chart based on Dawes' 
observations — shown here — showed it much more clearly, and others 
also represented it.* Schiaparelli represented the region well. My 
drawings at Meudon, confirmed by the photographs previously men- 

* 'Proctor's map,' wrote Schiaparelli, 'is not only much inferior to those of Madier 
and Kaiser, but does not even give an accurate representation of the observations of 
Dawes himself {Memoria I, 98). This chart is reproduced in Flammarion's La planite 
Mars, vol 1, a 05. In it Proctor shows an island to the right of Hellas that has not since 
been observed ; the Mare Acidalium is unrecognisable, and 18 too far north; the position 
of Elysium is 20° in error, and so on. 



87 



tioned, show Ausonia Australia broad to the S with Chersonesus, but 
narrower and rounded to the N, with the side turned toward the 
Xanthus inclined to the SSE (Fig 19), 

The albedo of this country is in general less than that of the conti- 
nents, as was noted as early as 1 862 by Kaiser and Banks. To me, the 
colour always seems intense when there are no Martian clouds around ; 
I see it as intense brick-red, sometimes fiery-red. 

When the planet appeared yellow in 1924, Ausonia Australis took 
on a magnificent, luminous coppery tint. On 11 November 191 1 I 
noted a small, brilliant patch near the centre. Ausonia Australis 
sometimes whitens under oblique lighting, and then appears clear and 
featureless; this was first shown by Schroter in 1798, 

With the o m, 83 on 6 December 1926 the region appeared to be 
whitish, protruding from the terminator. 

centauri lacus. In 1909, G. Fournier noted a dark spot on Ausonia 
Australis, near the middle of the coast of the Mare Hadriacum, which 
I confirmed independently several days later; I saw it again in 1924 
(Fig 19) and 1926. Superficially it is notably similar to our own Great 
Slave Lake. 

ausonia borealis, The lower part of Ausonia was drawn as a well- 
marked oval by Beer and Madler as early as 1830. I observed it, 
under perfect conditions, with the o™'83 in 1909, when it showed up 
as better-defined and more irregular than the S component ; there was 
a marked promontory to the NW (Fig 20). These features were con- 
firmed photographically by Hale and Barnard. 




Fig so Ausonia Borealis, very shaded; 20 September 1909. (o m -83 refractor) 



Ausonia Borealis is strongly marked, but is variable. Its greyness 
is recognisable on the drawings made by Schroter in 1800 and by 
Beer and Madler in 1830; it is striking on the 1909 photographs, 
where the albedo falls below that of the Mare Austral e. The colour, 
yellow according to Schiaparelli, seemed vivid rose to Cerulli; I saw 
it as dark brick-red in 1924, and in 1926-7 greenish (6 = 31° and 51 ) 
and later chestnut-coloured (e = 96 ). 

A patchy structure was seen here by Schiaparelli in 1 881-2. 

In 1892 my colleague, Quenisset, a very eminent observer, recorded 
a bright spot on Ausonia Borealis. 

I have never seen this region become white near the edge of the disk. 

On 12 October 1924, at Meudon, I saw a beautiful double pro- 
tuberance, with an intermediate darkish streak, at the terminator in 
this region. 

clROffiUM PROMONTORIUM (S, 1 877). This is the NE cape of Ausonia 
Borealis. It is very blunt, as is shown on the 1830 sketches of Beer and 
Madler, as well as on mine with the o m *83 (Fig 20) and on Hate's 
1909 photographs. 

POSIDIUM PROMONTORIUM. The NW cape of Ausonia Borealis, shown 
for the first time by Madler in 1830. Secchi drew it pointed in 1862, 
and I also saw this aspect at Meudon forty-seven years later (Fig 20). 

persa. In 1909, with the great refractor, I saw a tongue of irregular, 
smoky land, almost touching Ausonia to the W and S, and concentric 
with the Mare Hadriacum. It is comparable with our Lower Cali- 
fornia. Traces of it are found on the drawings made by Schmidt in 
1862 and Barnard in 1894. Hale and Barnard photographed this half- 
tone in 1909. I saw it again in 1911, 1924 and 1926. To me its colour 
seems dark reddish. 

The W border of Persea and Ausonia Borealis, sometimes made 
bright by Martian clouds, may at other times show a sort of 'optical 
bridge', recorded by J. D. Cassini as early as 1666, and which Lowell 
named Luna; Pons (Fig 61). 






anseris fons. Dark condensation on the Borbyses, well seen by me 
with the 0^*83 in 1909, 

coronas fons. Another similar feature, seen by me in the same 
year. 

mare hadriacum (S, 1 888). This is the Mare Hadriacum of 1877, 
which separates Hellas from Ausonia. It was one of the first patches 
to be discovered, because it is shown on the drawings made by 
Huygens in 1 659 and 1 672. It is again found on the drawings made by 
Herschel in 1783; by Arago in 1813, using the Emperor's o B1 'io2 
refractor, and by Beer and Madler in 1830, who represented it still 
better. Its detailed form, broad at the centre, was first shown by 
Schiaparelli; at Meudon I was able to confirm his drawings (Fig 19), 

The intensity of Mare Hadriacum is rather feeble, as was recorded 
on the lithographs by Kaiser and the drawings of Secchi, Lockyer 
and J. Phillips in 1862. This is how I have always seen it since 1892, 
and how it is shown on the photographs. Yet Attkins, Corder and 
Moles worth drew it dark in 1898-9, and it was sombre at the NE in 
1928-9. From 1896 to 1903 Molesworth believed that he had made 
out a more or less greenish-blue tint here (e = 6o° to 220 ); in 1909, 
with the o m *83, I saw a brownish colouration (e = 358 ), and in 1924 
(e m 337 ) I found the Mare to be a clear brown lilac. 

Mare Hadriacum was very pale, and covered with dusty material, 
in June, July and August 1907, according to Eddie, Hoskins, Buchanan 
and Shearer, and it seemed to be completely veiled by citron-yellow 
clouds at the time of the exceptional pallor of the maria in 1909, as I 
observed on 1 z August of that year at Juvisy. 

hellas (S, 1877). As with the preceding sea, this large island is a 
desert, comparable in area almost to our Greenland, and one of the 
regions of the planet which was recognised at the time of the first 
observations; indeed, we find its northern semi-circle on the sketches 
made by Huygens, mentioned above.* In 1830 Beer and Madler 

• This was established by Terby (Ariographie, 38). 

90 



showed the island elongated N-S, which is correct; and in 1864 
Kaiser found it divided into two lobes to the north, a peculiarity 
confirmed by Schiaparelli in 1877 and by myself in 1909 (Fig 21). 
This is in agreement with the photographs taken by Barnard and 
Hale. My drawings made with the o™'83 show the W lobe as being 
larger and extending farther north than the other, the upper part 
culminating in a 'parabola head*. In 1924, from Meudon, Hellas 
appeared to me to be rounder and of smaller perimeter than in 1 909, 
which confirms the fact that it is variable; this had already been 




Fig 21 Mare Hadriacum, ike red island of Hellas, and Yaonis Regio on 
20 September igoa, (p m -83 refractor) 

found by Schiaparelli, who in 188 1-2 recorded the island as being 
trapezium-shaped, and less extended than it had been in 1879. 

The ground of Hellas is not so bright as the continents; Schroter's 
drawings made as early as 1798 show it smoky. However, this shading 
is not uniform. It seems to attain its maximum to the south and its 
minimum to the NW, where a luminous patch is sometimes seen. 
Hellas is not an absolute desert, because its albedo is variable; in 1879 
Schiaparelli found that the quadrant turned toward Chersonesus was 
very strongly shaded, and in 1892 a large dark central patch was noted, 
which indicates a certain degree of fertility. (See Fig 22.) The colour 
of Hellas — red to Beer and Madler, reddish-yellow to Schiaparelli — 
seemed to me to be red in 1894; at this time Cerulli described it as 



91 



vivid rose. In 1909, from Meudon, it seemed brownish brick on 
20 September and red later; from 1924 to 1929, with the o m -83, I 
saw it as dull brick-red, sometimes with a very accentuated rose tint. 

Hellas is frequently covered by yellow clouds, particularly near 
perihelion; I saw this in 1924 as well as on other occasions. In 1881-2 
Schiaparelli believed it to be covered with a grey cloud. Moreover, it 
very often seems whitish when near the edge of the disk— or even 
brilliant white, like the polar caps— when Mars is a long way from 
the Sun. This remarkable phenomenon, recognised on drawings made 
by Herschel as long ago as 1777, made him show Hellas as protruding 
from the edge of the planet; this is due to irradiation, and is also 
observed with the polar caps. In 1877, on the other hand, Schiaparelli 
noted that in general the island was less white when near the limb ; 
but on 16 December 1877 and 4 March 1878 it was as brilliant as 
snow. In r88o, when the planet was a long way from perihelion, 
Schiaparelli, at Milan, saw the white margin of Hellas extend further 
and further toward the central meridian. From 1881 to 1890 Hellas 
often showed white at the edge of the disk, according to Schiaparelli; 
sometimes it was even as brilliant as snow. Since 1894 I have fre- 
quently seen it bright or white at the disk-edge, and sometimes it has 
even been brilliant. Moreover, on 20 July 1924 I observed Hellas 
covered with whitish tufts of cloud. On 19 February 1929 Giacobini 
and I saw the island very white near the time of sunset over it; we 
were then using the o m -38 equatorial of the East Tower of the Paris 
Observatory. 

Cerulli saw Hellas exceptionally bluish- white in 1896-7, and Danjon 
once saw it bluish-green in 1922. 

A great atmospheric disturbance extended over Hellas on 29 Septem- 
ber 1924, when I saw as yellow the two lower parts of this normally 
red land. The same aspect was seen on 3 October. On the 8th, Hellas 
seemed to protrude completely from the terminator, jutting out 20km 
to the N; and from the iqth to the 13th Baldet and I observed, both 
here and on Yaonis Regio, the projections described above. There 
were vast flocks of clouds, lying along the terminator and extending 
over a total length of more than 3,000km. 

92 



From 0-12 February 1927 Hellas and Yaonis Regio protruded 
from the sunrise terminator. 

PORTUS BUCOLEONTis. A small bay, observed by Kaiser in 1864 to 
the N of Hellas. Schiaparelli saw it in 1 877 and 1 879, and I confirmed 
its existence in 1909 with the o m, 83 (Fig 21). 

zea lacus. In 1892, Schaeberle and Stanley Williams independently 
noted a large dark patch in the middle of Hellas (Fig 22), to which I 
have given the name of Zea Lacus, Stanley Williams, who is the greatest 




Fig 22 



Large lake on Hellas, observed by Sckaberle on I July i8g2> 

(o m -gi refractor) 






English observer, has seen it with an 9™- 16 reflector— an admirable 
performance. To Schaeberle the lake appeared enormous, as it also 
did to Campbell in 1 894. In the latter year Maunder observed it with 
the o ra -7i Greenwich refractor. In 1909, 1911 and 1924 Zea Lacus 
seemed very pale from Meudon (Fig 21). Graff also showed it feeble 
in 1924, but in 1926 and 1928-9 it was again enormous, and eccen- 
trically-placed to the SE. It was just visible from Meudon when the 
apparent diameter of Mars was only 8* of arc. 

malea PROMONTORIUM. The name given to a cape jutting out to the 
S of Hellas. 

mare AMPHITRITES. This is the sea to the SW of Hellas, seen by me 
in 1924, with the o m *83, as of a striking brown chestnut colour (e = 
18 ). 

pityusa insula. On 8 December 1924 I saw a narrow land in the 
Mare Amphitrites, curved parallel to the coast of Hellas. 



93 



nerei depressio. Dark patch to the W of Hellas, in the Mare 
Amphitrites, striking with the o 01 ^ in 1926. 

YAONIS FRETUM. Curved strait separating Hellas from Yaonis Regio. 
Madler showed it as early as 1 830. From Meudon, in 1 909, it seemed 
to me sombre and narrow to the NE, but degraded and broader to the 
SW (Fig 21). I saw it very dark in 1926. 

yaonis regio (S, 1 879). Well-marked dark, patchy area to the NW 
of Hellas, drawn for the first time in 1830 by Beer and Madler. 
Lassell represented it faithfully in 1862 with his i™-22 reflector. With 
the o m -83, in 1909, it seemed to me slender to the NE, but plainly 
rectangular and concave towards Hellas, fading away toward the S 
(Fig 21). It is strongly smoky in hue, even more so than Hellas, as 
was shown as early as LasseH's observations; the 1909 photographs 
show an albedo a little higher than that of Ausonia Borealis. From 
Meudon, it always appears a definite brick-red. 

The cloudy protuberance observed here in 1924, and which veiled 
the lands nearby, has been described above. On 23 January 1925 I 
noted a yellow salient on the morning terminator in the region of this 
island; and from 9-12 February both Yaonis Regio and Hellas seemed 
to protrude from the sunrise terminator. 

hellespontus (S, 1 877). This is a strait 2,500km long, separating 
Hellas from Noachis. Herschel represented it as early as 1779. Secchi 
showed it branched in 1862, and Kaiser as double; I confirmed this in 
1924, when the left branch of the channel formed the SW prolonga- 
tion of Yaonis Fretum. These arms of the sea showed up as filamentary 
from Meudon in July 1924,* and narrow to the N in 1926. 

The intensity of Hellespontus is very variable. Though Herschel 
did not record it in 1781 and 1783, Schroter in 1798 found it as blackish 
as the Sinus Saba?us, which is astonishing, f Then, in 1800, the channel 

"In 1877 Green drew a 'Kunowsky Land* on Hellespontus, but this has not been 
confirmed by later observations, 
t This has been shown by Terby (Ariographie, 43). 

94 



was often invisible to the Lilienthal observer. Beer and Madler did 
not see it in the S in 1830 and 1832; but according to Kaiser, Lassell, 
Banks and in particular J. Phillips, it seemed intense in 1862. Holden 
saw it sombre in 1875; but it was pale in 1877, according to the 
Henry brothers, Schiaparelli, Green and Harkness, and also in 1879, 
according to Terby, Niesten, Burton, Lohse, de Konkoly and Schia- 
parelli. In 1892 Campbell saw it dark. I saw it equally intense in 1894 
(Fig 23), and Lowell and Lampland photographed it as large and well- 
marked in 1907. With the o m, 83, I found it feeble in 1909 and 191 1, 







Fig 23 The dark Hellespontus, on 29 August 1894. {Juvisy o m -24 refractor) 

dark at the beginning of the opposition of 1924, pale in 1926. From 
these data it seems that Hellespontus often appears sombre between 
e =■ 260 and 30 , and pale afterwards. To me it seemed clearly brown 
in the great refractor in 1909, 1924 and 1926 (e = 358 , 29 1° to 36 
and 28 ). 

Yellow clouds veiled this channel almost continuously, though 
feebly, at the time of the great pallor of 1909. The concealment was 
total in January 1925, according to my observations with the o m -83. 

helles depressio. Dark patch, which I saw from Meudon to the 
S of Hellespontus in 1924. With the o m -83 it seemed very dark in 
1928. 

noachis (S, 1877). Recognisable on a drawing made by J. Herschel 
in 1830, this island was not well represented before the work of 
Schiaparelli, because its boundaries are so diffuse. It is best defined 
at the border with Hellespontus, and its curved form appears to be 



95 







Fig 24 The red land of Noachis, on 23 October 1909. (0^-83 refractor) 

broadly lenticular (Fig 24). When Pandora; Fretum is visible, Noachis 
is well defined to the N; but when Pandora; Fretum is invisible, 
Noachis extends up to Deucalionis Regio. Schiaparelli drew Noachis 
small in 1877 and 1879; but it was almost as big as Hellas in 1924, as 
seen from Meudon. On 8 December 1928 I was very surprised to see 
Noachis invaded to the N by an oblique band, as dark and broad as 
the Sinus Sabseus, and emerging to the SW of the Mare Serpentis 
(Fig 25). Our colleague M Schlumberger observed it from the 6th, 
and it had been well seen in January with the great Meudon refractor 
by Mme la Duchesse de La Rochefoucauld. This was a change un- 
precedented in the history of Mars. At the Paris Observatory, on 




Fig 35 Noachis, invaded by a grey, dark streak, twice as extensive as 
France, observed on 8 December 1928. (o m -83 refractor) 



19 February 1929, Giacobini and I found that this extraordinary streak 
was darker than the Sinus Sabzeus itself. The observation was made 
with the o m '38 equatorial of the East Tower. The aspect was still the 
same on 30 March 1929. 

The albedo of this desert is still below that of the continents, at 
least that of Hellas. This is confirmed by the photographs. The half- 
tone was indicated as early as 1798 by Schroter; J. Herschel in 1830, 
Kaiser in 1862 and many others showed it later. I have almost always 
been able to record it since 1892, Secchi found Noachis red; Schia- 
parelli, dark yellow. From Juvisy in 1894 it seemed brick- red, and 
with the o ro, 83 it has, in general, been smoky-red-vermilion, with an 
occasional rose tint. During the invisibility of Pandorae Fretum from 
June to October 1924, the physical appearance of Noachis was curious; 
the vermilion hue extended north to a point bordering on the grey tint 
of Deucalionis Regio. 

In 191 1, from Meudon, yellow clouds sometimes bronzed Noachis, 
effacing all trace of red ; this was noted by Bosler and myself. As with 
Hellas, Noachis often shines with a whitish brilliance on the termi- 
nator, especially when Mars is a long way from perihelion. This phe- 
nomenon was well indicated on the drawings by Secchi made in 1858, 
by Kaiser in 1862, and on the pastels by Trouvelot, using an o m -38 
refractor in 1873. Seldom brilliant to Schiaparelli from 1877-82, it 
often appeared white to him, and sometimes even brilliant, from 
1883-90. I have sometimes observed it brilliant at aphelic oppositions, 
as on 15 and 18 December 1926. In October 1877, from Milan, it 
was seen to be covered with clouds, as if following a tempest ; and on 
9 September 1926 the island was whitened in the NE. 

In violet light, Le Morvan photographed a whitish cloud over 
Noachis on 19 October 1909, with the great equatorial coude of the 
Paris Observatory. 

Some luminous projections were noted on the terminator at 
Noachis, to i°, by Hussey and Campbell from 2-17 July 1892; to 2° 
by Flammarion and myself at Juvisy, from 20-2 August 1894; and to 
3° by myself at Meudon, on 22 January 1925, when I saw there a vast 
yellow projection on the sunrise terminator. 



96 



97 



On 2 January 1897, the skilful observer T. E. R. Phillips noted a 
protuberance on the terminator, lying on the W part of Noachis. 

arietis PROMONTORIUM. The NE tip of Noachis, recognisable on a 
drawing made by Schr6ter in 1798 and on one by Beer and Madler 
made in 1830. In 1924, from Meudon, it was striking (Fig 27). 

fandqrje fretum. The vast strait sometimes separating Noachis 
from Deucalionis Regio, comparable to a sort of Mozambique Canal. 
It was drawn three times by Herschel in 1783. My drawings made 
from Meudon in 1909, confirmed by the photographs, show it as 
broad as the Sinus Sabseus, going up again toward the SW, 

The very variable intensity of Pandoras Fretum, noted by Flam- 
marion (La plankte Mars, vol 1, 179) is curious; sometimes it rivals 
that of the sombre Sinus Sabaeus, only to fall subsequently to that of 
the brick vermilion of Noachis, Thus the arms of this sea appeared 
very dark in 1783 to Herschel, and in 1798 to Schroter, Beer and 
Madler did not record it in 1830 and 1832; in 1858, Secchi saw it 
sombre; in 1862, J. Phillips showed no trace of it; in 1864, Kaiser 
represented it as intense; in 1875 it was again invisible to Holden. 
In 1877 the Henry brothers, Schiaparelli and Green saw it intense; 
in 1879 Burton and Niesten drew it as only slightly shaded. The aspect 
was much the same from 188 1-4 to Schiaparelli, but in 1890 it was 
feeble as seen from Milan. In 1892 it appeared very feeble to Keeler, 
and in 1894 to Maunder and myself; to me this pallor persisted until 
1907, At this latter date Nangle could scarcely make it out. In 1909 
I found it very sombre (Fig 26); in 191 1, invisible; from 1913-16, 
very feeble. Danjon hardly ever saw it in 1922. Then, in 1924 — in 
agreement with my predictions* — it was at first pale (Fig 27) and 
then, after opposition, darkened. In 1926 my predictions about its 
intensity! were equally well verified ; Pandora; Fretum was very dark. 
Finally, in 1 928 I could barely, see it in the o m -83 (Fig 25). 

Correlating these observations with the Martian seasons, it appears 

• Bull Soe Astr d* France, vol 38, 1924, 200. 
f Ibid, vol 40, 1936, 378. 



98 




Fig 26 {1909) and Fig 27 (1924) Changes observed on Pandora Fretum 

{o m -8s refractor) 

that Pandorae Fretum often shows up as dark between e ■ 340 and 
30 , but is almost always feeble or invisible between e = 40 and 300 . 
In my view, we have here a periodical though slightly irregular 
seasonal variation.* 

I noted the channel greenish in 1909 (e = 3 5 8° to 20 ); then patchy 
and greenish or violet-hued in 1926 (e = 8°) and later m the same year, 
brownish violet (e = 28 ). 

In 1924 I watched the greyness developing on the red soil, which 
seems to indicate fertility. 

At the time of the pallor of the seas in August 1909, Pandorae 
Fretum was veiled by yellow clouds, and was scarcely visible. 

dori depressio. Sombre condensation in Pandorae Fretum. I saw 
it from Meudon in 1926. 

xuthi depressio. Another condensation observed here in 1926. 

mare serpentis. The Sinus Sabaeus sometimes appears prolonged 
to the SE by a very dark streak, curved like a serpent; this is the 
'Serpentino' of Schiaparelli (Memoria, vol IV, 15). Mare Serpentis, 
represented by Huygens as early as 1659, was well drawn by Madler 
in 1830 as being turned back toward the W to Hellespontus, and 
forming a gulf on Noachis. The drawings made in 1862 and 1864 by 
Kaiser confirmed this aspect. In 1877 Dreyer, and more especially 

• Mm Report for 1915-16 in BAA Mem, vol 21, 1920, 9011. 



99 



the Henry brothers, successfully observed this region, as did Niesten 
and Schiaparelli in 1879. Subsequently, Mare Serpentis appeared 
striking to Cerulli between 1896 and 1899. In 1924 I was very sur- 
prised to see this dark feature turn to the W of Hellespontus, going 
up again a little beyond the S limit of Pandorae Fretum, and strongly 
notching the enormous red mass of Noachis (Figs 27 and 28). This 
aspect has since been confirmed by the beautiful photograph taken 
by Hubble with the 2 m -57 Ritchey mirror at Mt Wilson. In 1909 Mare 
Serpentis was green (e = 3 5 8°); in 1926, very dark and violet (e = 51°), 
while in 1928 it appeared very dark grey or blackish (e = 83°). 




Fig 28 Mare Serpentis and Sinus Sabeeus, 22 August 1924. {p m -83 refractory 

The intensity of Mare Serpentis is very great, sensibly equal to that 
of the Sinus Sabaeus ; it was thus shown on the drawings of Lockyer 
and Kaiser, and on the photographs. In 1928-9 it was blackish, 
darker than the Sinus. However, when Pandorae Fretum is dark, the 
whole configuration here is transformed. 



OFHiucm SINUS. This is the gulf to the SW of Mare Serpentis. 
is very striking on Midler's drawings, and on mine of 1924. 



It 



scylla and charybdis (S, 1877). Between the cape E of Deucalionis 
Regio and Iapygia, there is a broad dark strait (Fig 1 6), also found on 
Huygens' sketch of 1659. It was named by Schiaparelli. In 1909, as 

100 






seen from Meudon, the region was green (e = 358°); in 1926, violet 
(e = 28 to 32 ). 

deucalionis regio (S, 1877). This great longitudinal island, the 
shape of a cigar, runs nearly parallel to the equator between Pandora 
Fretum and the Sinus Sabseus. Defined for the first time by Herschel 
in 1783, it has since been seen by nearly all observers. However, Beer 
and Madler did not draw it well, and it was only in 1858 that its 
form was fairly accurately shown by Secchi. In 1862 Kaiser's drawings 
placed it accurately, pointed to the E and curving back at a right angle 
at the N, on Thymiamata. This configuration, which escaped Dawes 
and Green, is normal; it is in agreement with the 1909 and 191 1 draw- 
ings from Meudon (Fig 29) and with the photographs taken in those 
two years. The stralghtness of the island shows the effects of diffrac- 
tion, Deucalionis Regio appears straighter in a large instrument than 
in a small one, and proportionally straighter when Mars is close than 
when it is remote. The bend on Thymiamata varies in breadth; 
narrow to Lockyer in 1862, it always seemed to Schiaparelli as broad 
as the head of Thymiamata, but it was not shown as very much ex- 
tended on the drawings made in 1 881-2 by Boeddicker, in 1892 by 
Schaeberle and in 1894 by Campbell. The 1909 photographs show it 
as in the Milan maps. In 1924, however, Baldet again saw it narrow, 
and I soon confirmed this (Figs 43 and 68); the narrowness was also 
corroborated by Hubble's photograph, mentioned above. To the E 




Fig 20 



Deucalionis Regio, with Sinus Sabeeus, 16 October igog. 
(o«-Sj refractor) 



101 



side Deucalionis Regio sometimes appears broad; 'this was how Schia- 
parelli and Stanley Williams noted it in 1890. In 188 1-2, Boeddicker 
drew the S boundary of the island as ragged; and in 1909, from 
Meudon, Idrac observed the island 'cut up into a great number of 
capes and gulfs of very clear colours' — an important observation. 

In 1896 Molesworth, and in 1909 the Henry brothers, drew Deu- 
calionis Regio cut through by dark, more or less vertical, shafts. I 
confirmed these from Meudon in 1924. 

This desert island is much less luminous than the continents to the 
N, as was shown on Schroter's drawings as long ago as 1798. The 
albedo is inferior even to that of Noachis, particularly in the NW part, 
beyond the middle of Sinus Meridiani up to Thymiamata — which is 
here at its darkest (Figs 29 and 43). Kaiser was the first to show this, in 
1862. This darkening to the right is also shown on a beautiful photo- 
graph taken by Hale in 1909 with the i m *52 Ritchey reflector at Mt 
Wilson. In 1924 I noted the same thing with the o m> 83 refractor, and 
the aspect was confirmed on Hubble's photograph mentioned above. 

Deucalionis Regio is sometimes reddish, sometimes greyish, as was 
noted by Schiaparelli. 1 Secchi noted it as yellow in 1858, and so did 
the Milan astronomer in 1879, 1883-4 ana< '886; in 1888 it appeared 
yellowish grey-brown to Schiaparellt ; in 1890 ashy and smoky, some- 
times brownish-yellow. Stanley Williams saw it white at this time. In 
1896-7 Cerulli noted it sometimes reddish, sometimes greyish. At 
Meudon, in 1909, I saw it as ashy on 20 September, very red on 19, 
21 and 23 October; in 191 1, red on 3 November, grey on 6, 7 and 8 
November and it, 14 and 15 December; in 1924, I judged it red 
only on 19 and 20 July, and greyish from August to December. 
Finally, in 1926 it was red on 6 August and 9 September, grey on 
8 October, red on 13 October, grey on 18 and rg October, and 
reddish on 26 November. It seems that the soil here is red, and 
that the greyish aspect could be of atmospheric or even volcanic origin. 

Browning in 1867, and Douglass in 1894, sometimes noted a green- 
ish tint on this island. 

Though sometimes veiled by yellow clouds, Deucalionis Regio has 
sometimes been seen clearly in spite of the interposition of whitish 



102 



clouds; this was shown by Kaiser in 1864 and by myself sixty years 
later. The land does not appear white under an oblique view as often 
as Hellas or Noachis; but the phenomenon was observed by Schia- 
parelli in 188 1-2, and I have since confirmed it. 

DiuM PROMONTORIUM. This is the E cape of Deucalionis Regio, 
which Herschel drew as early as 1783, and which from Meudon 
appeared blunted in 1924 (Fig 43) and 1926. 

ara. A half-tone which is delicate and seldom visible, joined on to 
Hammonis Cornu. It can be found on Kaiser's drawings of 1862 and 
1864. In 1896-7 Cerulli showed here a triangular smoky land, noting 




Fig 30 (20 September 1909) and Fig Ji (27 August 1924) Temporary 
visibility of the half-tone of Ara. (o m -83 refractor) 

that it was 'sometimes bright, sometimes obscure'. 8 In 1898-9 Kemp- 
thorne, Molesworth and Phillips confirmed this. From Meudon, I 
saw nothing of the kind in 1909 (Fig 30), but on 27 August 1924 I 
was struck, as was Baldet, by a sort of yellow tongue emerging from 
Hammonis Cornu and extending to the SE (Fig 31). This ooject was 
less obvious later, as Graff noted on 2 September. It was not well seen 
in 1926 or 1928. 

STRONGYLl insula. Circular, lightly shaded island which I noted 
in 1909, from Meudon, in the green tracts in this region (Fig 30). In 
1924 it made up part of Ara. These two objects sometimes give way 
to the appearance of a bright ligament joining Hellas to Hammonis 
Cornu, first drawn in 1862 by Lord Rosse's observer with the i m -83 
reflector, and named Solis Pons by Lowell. Strongyle Insula was 
greyish in 1909, red in 1926. 



103 



mare ionium. This is the sea lying to the N o£ Yaonis Regio, shown 
on the sketch made in 1659 by Huygens, Browning called it green in 
1867, Lowell brown in 1903 (e = 197 to 199 ). It was green to me 
from Meudon in 1909 (e = 358 ) ; in 1934 1 found that it still remained 
green on 8 December (e = 36°), resisting the brown discolouration of 
its neighbouring areas, and in 1926 it was still green (e = ii° to 32°). 

DEPRESsio ionica. This is a dark patch in the sea N of Hellas. Those 
eminent observers Beer and Madler were the first to represent it, in 
1830. It was subsequently drawn by Brodie in 1856, by Cerulli in 
1896-7 and by myself in 1898-9 at Juvisy and ten years later at 
Meudon, while at the same time Hale and Barnard photographed it. 
With the o m -83 I saw it again in 191 1 (Fig 37) and in 1924 and 1926; 

I saw it again in 1927 when Mars had an apparent diameter of 8"*o. 

iapygia viridis (S, 1877). In 1 858 Secchi drew a bright region 
below Hellas. 8 This pale, indefinite half-tone was later represented by 
several observers, notably by Trouvelot, Green and Schiaparelli, who 
followed it until 1890; by Burton in 1882, Hussey in 1892, Campbell 
and myself in 1894 and Eddie in 1907. The photographs taken in 1907 
by Lowell and Lampland, and those of Barnard in 1909, show the 
patch as feeble, and closer to Hellas than to Syrtis Major; but on 
Hale's photograph, Iapygia is less evident. In 1894, with the o m *9i 
Lick refractor, Barnard described 'a mountainous country seen to have 
considerable height'. On 20 September 1909 (e = 358°), with splendid 
images with the great Meudon refractor, I was struck by the panoramic 
view of these Martian landscapes; I could see all the magic of its 
details, with the colouring of the woody clumps, and the green 
vegetation speckled with tiny white points — producing an unforget- 
table impression. As early as 1888 the greenish tint of the region was 
recognised by Holden (e = 257 ). In 1924 the green was still there on 

II October; but on 8 November (e = 18 ) there was only lilac-brown, 
as was seen (in my absence) by Baldet. It is because of this very vivid 
green colour that I have added the adjective 'Viridis* to the original 
name. 



104 






Schiaparelli found Iapygia billowy in 1879 and granular in 1881-2. 
At the latter opposition, it was seen whitish when near the limb. 

CENOTRIA (S, 1877). Another smoky, variable half-tone; it is often 
easily visible in the middle of the Syrtis, and was clearly shown for 
the first time on the 1830 drawing by J. Herschel mentioned above. 
It is joined on to the Nymphaeum Proraontorium, and sweeps in a 
graceful curve toward Ausonia. De la Rue saw CEnotria in 1856, but 
Secchi did not record it at all in 1858 or 1862. Kaiser drew it clearly 
in 1864, but it was again omitted by Trouvelot and Green in 1873. 
Easy to Schiaparelli in 1877 and 1879, it was glimpsed in the latter 
year by Terby with an o m - 108. Schiaparelli observed it again in 188 1-2, 
but could not see it in 1883-4. I* 1 1886 it seemed to him to be very 
much in evidence; but in 1888 and 1890 he drew it as reduced and 
transformed, and cut off to the E. I saw this in 1892 with an o m -io8; 




e.M.A. 



Fig 32 Syrtis Major, with CEnotria, the Sinus Sabceus and 
the lakes to the north, seen on 5 April 1903 (fi m -2i6 reflector) 

I also observed it in 1894, though with difficulty. It was easier from 
1896 to 1899, and much easier in 1900-1. My o m -2i6 reflector showed 
it as large and diffuse in 1903, feeble in 1905. Then, in 1907, Eddie 
found it very clear; Givin saw it in an o^-og. With the o m *83, I saw 
it well in 1909, but it was feeble in 191 1. From 1913 to 1916 Phillips 

105 



and Thomson showed it as being normal. It was striking to Danjon 
in 1922, feeble to me from Meudon in 1924; but more marked in 1926, 
and strong in 1928. (Enotria was photographed by Lowell and Lamp- 
land in 1905 and 1907. 

incurva INSULA. On 20 September 1909, marvellous images with 
the o m, 83 allowed me to see a very narrow whitish island curved 
back and crescent to the SE, extending from Hammonis Cornu to 
Nymphseum Promontorium (Fig 40). It also extended to the E of 
Deltoton Sinus, and was completely detached from the green patches 
in these regions. It is probably permanent, because it was shown on 
drawings made by Trouvelot in 1873, Green in 1877, Bceddicker in 
1 88 1-2 and Campbell in 1894. Barnard succeeded in photographing it 
in 1909. In 1926, the island was red as seen from Meudon. 

MARE TYRRHENUM (S, 1 877). By this name Schiaparelli indicated the 
vast sea which extends from the Xanthus to Meroe, along more than 
5,000km in length, and of which the two Syrtes are no more than gulfs. 
The W part of it can be seen on the sketches by Huygens mentioned 
above; the E part is visible on the drawings made by Bianchini in 
1719. Its general form was well sketched by Beer and Msedler in 1830. 
Schiaparelli made out more details in the area in 1877 and 1879. 
From Meudon, in 1924, I was able to study it to advantage; at first 
it showed a triangular head below the Xanthus, then retraced its steps 
and became convex toward the NE and then, in the region of the 
Euripus II, opened toward the W in a rectangular gulf. Subsequently 
it broadened somewhat, and became concave to the SW, forming 
Syrtis Minor to the NE and debouching into the Syrtis Major. The 
form resembled that of the island of Euboea. Several observers, in- 
cluding Lassell in 1862, reported numerous pointed gulfs here, but 
these remain unconfirmed. Mare Tyrrhenum does not seem to have 
changed much during the past century. 

It is often very dark, more so than the Mare Cimmerium. However, 
its intensity is less uniform than with any comparable sea. As early as 
1900 to 1903 Molesworth, a skilful observer, found Mare Tyrrhenum 

106 




Fig 33 The Mare Tyrrhenum, seen as speckled on 20 Septem- 
ber 1909 (o m -83 refractor) 



patchy, and in 1 909, with the Meudon refractor, I saw it as an unequal 
structure, composed of about 16 sombre nuclei, giving Mare Tyrr- 
henum the appearance of a leopard-skin — or, if you like, a gigantic 
chess-board! 4 In 1924 Baldet confirmed this patchy structure, as did 
that excellent observer Danjon in 1926, using a magnification of 750 on 
the o m, 49 Strasbourg refractor. The colour seemed greenish to Holden 
in 1888 (e = 257 ); in 1909 (e = 358 ), with the o m -83, I saw it olive 
green; in 1924 (e = 336° and over) Baldet recorded it as brownish, 
while I also noted a faint violet tint; subsequently the colour was faint 
violet, sometimes obviously so; and in 1926 it seemed at first to be 
greenish (e = 352 ) and then, to me, brown lilac (e = io° and 14 ). 

At the time of the great pallor of summer 1909, there were several 
days when I could hardly see the Mare Tyrrhenum at all. In 1924 the 
left part was veiled before 1 August, and in December the whole sea 
again became almost invisible with the o m -83. In 1879 Schiaparelli 
and Burton observed a bright shifting spot here, apparently dividing 
up the sea; and on 14 October 191 1, from Meudon, I saw a vast white 
cloud, exceptionally opaque for Mars, totally obliterating the Mare 
Tyrrhenum even in this great instrument. 

procyonis DEPRESsio. This is the southernmost of the dark patches 
of the Mare Tyrrhenum seen by me in 1924 with the o m *83- 

107 



APODis DEPRESSIO, The easternmost of these patches to the south of 
the Mare. 



ledje, pons. A sort of bright ligament, dividing Mare Tyrrhenum 
down the middle, towards the Euripus II; it was observed in 1877 by 
Harkness, with the o m -66 refractor at Washington. As it was also seen 
in this year by the Henry brothers, and later by myself with the 
o m, 83 in 1909 (Fig 33), 1924 and 1926, it seems to be permanent. 
Hale even managed to photograph it in 1909. 

syrtis minor (S, 1 877). Also called Syrtis Parva. This important 
bay in the Mare Tyrrhenum was drawn vaguely by Schrceter in 1798 
and by Beer and Maedler in 1830; Secchi, in 1858, drew it more faith- 
fully. I have always been able to see it from Meudon (Fig 33), which 
is in agreement with the 1909 photographs by Hale and Barnard. 

In 1888, Schiaparelli found the bay enlarged at the expense of Libya. 

Syrtis Minor is sombre, so forming one of the dark nuclei in the 
Mare Tyrrhenum. Its colour appeared green to Douglass in 1894. 
(e = 325 ), bluish to Molesworth in 1903 (e = ±190°). In 1909, from 
Meudon, it was olive (e = 358 ); in 1924 (e = 336 ) it seemed at first, 
to me, to be brownish-violet and then greenish, becoming purple in 
October (e — 2 ). In 1926 it was green to begin with (e = 350 ), 
passing into brownish-violet later (e = io° and 14 ). 

To me, the bay seemed to be very feeble from 1892 to 1901, and 
again in 191 1 ; when I began my observations in 1924 it was the same 
orange colour as the continents which were concealed by yellow 
clouds. 



crocea. A half-tone prolongation toward the SW from the pro- 
montory extending into Libya can sometimes be seen, interrupting the 
lower part of the Marc Tyrrhenum. I have named this temporary 
object Crocea. Maedler observed it with his second refractor (the 
o m -24) in 1841; subsequently Kaiser showed it in 1864, Burton in 
1882, Keeler in 1892, Millochau in 1903, and others later. It is shown 
on Graff's drawings of 191 1, when to me it appeared striking (Fig 37); 



108 



it was also prominent in February 1927 and December 1929. These 
data prove that Crocea becomes bright from time to time. 

syrtis major (S, 1877). Also called Syrtis Magna. This famous 
dark patch, otherwise known under the name of the Hourglass Sea,* 
and serving as a 'clock-hand* for determining the rotation period of 
Mars, is the first dark marking to have been observed on the planet. 
It is the 'Atlantic Channel' or 'Scorpion' of Schiaparelli, recognisable 
on the sketches made as early as 1659 and 1672 by Huygens." J. D. 
Cassini and Hooke drew Syrtis Major in 1666. It forms a great gulf 




Fig 34 



Seasonal variations of the eastern areas of Syrtis 
Major 



pointing to the N, with dimensions almost as great as those of the 
Gulf of Bengal ; and thanks to its very dark hue, it is the most easily- 
seen patch on the entire planet. Maraldi the elder showed it as tri- 
angular in 1 71 9. From the following side, where its shores appear to 
have remained almost unchanged for the past two and a half centuries, 
it is penetrated by the Nymphasum Promontorium; on the preceding 
side, however, the contour shows changes. 'The Syrtis Major,' wrote 
Schiaparelli in 1879, 'has invaded a region which belonged to Libya 
in 1877,'* when this vast sea appeared exceptionally narrow. In 1881-2 
Schiaparelli referred to 'the progressive invasion of Libya by the 



* Because of its V-form, supporting a reversed and lighter V made up of the patchy 
lands to the north. 



109 




Fig 35 1905, Lamptand. Fig 36 1909, Hale, 

Seasonal variations of Syrtis Major, according to the 
American photographs 



breadth, and at the beginning of the observations in 1924 (e = 288 ) it 
was broad, though it diminished considerably until 8 November 
(e = 18 ). In 1926 it appeared broader; in 1928, the same. These 
conclusions were confirmed by the American photographs (Figs 35 
and 36). At the N coast Syrtis Major appears pointed when seen in 
small instruments, blunt with larger ones ; toward the NW there is the 
little bay of Astusapis Sinus (Fig 37). 

The intensity of Syrtis Major, although so marked, is not uniform. 
It is greatest at the N point, as shown on the drawings made by 
Huygens and Schrceter; this is probably an effect of contrast. The 



Syrtis Major', 7 Then he favoured a continued diminution of Libya 
from 1877 to 1884, and 'a constant state from 1886 to iSgo'. 8 In 1899, 
Douglass thought that 'the changes in this region appear to be secular 
rather than dependent on the seasons', and that 'though seasonal 
variations probably exist, there is nevertheless a marked difference in 
the aspect at the same season but in different years'.* My examination 
in 19 1 6 of the drawings of the Syrtis Major made since the time of 
Secchi showed a very clear periodical variation, by no means secular. 
Thus this great sea appeared narrow after perihelion in 1862, 1877, 
1892, 1909 and 1924, and broad after aphelion in 1858, 1873, 1890, 
1905 and 1918. The maximum narrowness seems to occur, on average, 
around e = 15 ; after e = 70 the Syrtis broadens, attaining its greatest 
breadth around e = 230°, and there is a rapid diminution around 
e = 290 . At the time of its greatest extent, Syrtis Major appears 
arched to the E, forming a gulf toward the MtEris Lacus (Fig 34, 
contour ADC); on the other hand it is concave at the time of its 
greatest retreat (Fig 34, ABC). It is thus subject to a periodical 
darkening (a in Fig 34), becoming greenish when it is sombre; 
Secchi wrote in 1858 that 'the great blue channel is accompanied by 
a greenish band to the left'. 10 The observations made at Meudon over 
a period of a quarter of a century give an accurate picture of these 
metamorphoses. In 1901 (e = 153 ) Millochau drew it as very broad, 
and forming a bay in the Mceris Lacus (Fig 64); in 1909 (e = 358 ) 
I saw it very narrow (Fig .39); in 191 1 (e = 53 ) it had increased in 



110 







6. M. 6 



Fig 37 General aspect of the Syrtis Major and its neighbourhood, 
on 13 November 1911 (fl m -83 refractor) 

whole gulf sometimes sombre over a polygonal area, pointed to the 
S, while the regions above remain pale; this is shown on the drawings 
by Terby and Holden in 1875, by Schiaparelli in 1890, Keeler in 
1892, Jarry-Desloges, G. Fournier, Givin and Eddie in 1907, and 

111 



Quenisset and Danjon in 1922 (Fig 38). We are dealing here with a 
very enigmatical seasonal phenomenon, which is most evident between 
e = 260 and 320 . Also, the W coast seems darker than the E coast; 
this is another contrast effect, because the former borders upon the 
bright continent of Aeria, while the latter adjoins the greyish areas of 
Libya and Isidis Regio. This inequality of tone is recognisable on 
sketches made by Herschel as early as 1781. Moreover, the dark 
border is sometimes attenuated near the lower part by the temporary 
visibility of the half-tone of Arena, The colour of Syrtis Major was 
estimated as blue by Secchi in 1858 (e = 250 ), green in the S by 
Holden in 1888 (e = 257°), clear greyish blue-green by Molesworth 
from 1896 to 1899 (e = 6o° to 150°) and bluish grey-green by Moles- 
worth from 1900 to 1903 (e = 130 to 220 ). In 1909, I found that the 
whole area to the N of (Enotria was bluish-grey, while the region to 
the S was patchy green (e = 358°). In 191 1 (e = 57 ) it appeared 
grey-indigo to me at Meudon; in 1918 (e = 160 ) it was blue to 
Quenisset and then (e = 178°) greenish-blue to Thomson; in 1920 
(e = 215 ) it showed as blue, with a steely tint, to Gale. Using the 
o ra -83 in 1924, I saw a colouration similar to that of 1909 up to 
November, but on 7 December (e = 18 ) Baldet found that the colour 
had changed to brownish-violet, and I confirmed this on the 8th. In 
1926, I first noted a greenish hue (e = 349 }, then greenish and 
brownish (e = n°) and later, brownish-violet (e = 32°). Lastly, in 
1928 (e - 86°) it appeared greyish-green. It seems, then, that the 
Syrtis normally appears bluish-grey, sometimes with traces of green ; 
but it becomes brown near io° heliocentric longitude, remaining 
brown for a short time up to around 40 heliocentric longitude before 
again becoming bluish-grey with an occasional tint of light green. 

After a good observation made on 3 1 January 1869 with Lord Rosse's 
great o m "9i reflector, Burton wrote: 'Many details were visible, the 
most remarkable being the almost blackish points, excessively faint 
and abundantly distributed over the southern (upper) part of the neck 
of the desert region ; their visibility was evidently because I was using 
a large aperture.'" In 1896-7, at Juvisy, I also saw a patchy structure 
in the Syrtis (Fig 61), confirmed at the same time by Kempthorne, 

112 



and also by Molesworth from 1900 to 1903 and by Porthouse in 1914. 




Fig 38 Syrtis Major, dark to the north, very pale to the 

south, vtith a lake near the estuary of the Astaborus, seen on 

7 July IQ22 (o m -^o refractor) 



It is on record that a dark point was noted to the S of this sea by 
Schiaparelli in 188 1-2. 

Cloudy veils are frequent in this region. Thus Msedler found the 
Syrtis Major pale in 1 837, and on one occasion in 1 884 Bone drew it 
as more feeble than the Nilosyrtis. Then in August 1909, with Quenis- 
set, I found that it was virtually invisible — a ghost of itself even when 
on the central meridian, covered with citron-yellow clouds as seen 
with Flammarion's o m -24 telescope at Juvisy! The same aspect 
persisted until the 1 5th ; this was the greatest obliteration which has 
ever been observed. On 12 October 1924, using the o m -83 together 
with Quenisset, I found that the Syrtis Major could not be seen, 
its place being taken by a greyish-yellow mass. It was even more 
enfeebled at the time of the great pallor of the seas in January 

A belt of whitish clouds, parallel to the equator and separating the 
Syrtis from the regions to the S, has been observed more than once. 
This basic aspect was drawn by various observers, including Burton 
and Gledhill in 1871, Lohse in 1873, Kibbler in 1 900-1, Gale and 
Denning in 1903, and H. Wright in 1905. 

On 7 June 1858, Secchi wrote of the Syrtis: 'The main part of the 
dark patch is crossed by white veils ! What are they? On the 1 5th, they 
could no longer be seen.' And the Roman astronomer added: 'We 



113 



may have seen the great patch of the Atlantic Channel as if covered up 
by cirrus.' 1 * 

nili syrtis. This is the blunt, dark lower gulf of the Syrtis Major. 

astusafis SINUS. The port of the Astusapes on the great sea is shown 
on a sketch made by Schroeter in 1798. Secchi drew it in 1858, 
Schiaparelli and Burton in 1 879 ; others have seen it since. At Juvisy, 
it appeared small to me in 1900-1. In 191 1, using a power of 810 on 
the Meudon refractor, I saw it as very slender (Fig 37). 

astabofje sinus. In 1930, G. Fournier was the first to note a large 
extension of this bay, taking the form of a blackish lake toward the 
W; it was soon confirmed by Ellison, Gale, Thomson and Phillips, 
and was again corroborated by Danjon in 1922 (Fig 38). 



arena. Rarely visible, temporary half-tone, in the N part of the 
Syrtis Major. It was first observed by Cerulli in 1898-9, and in 1901 
and 1903 it was seen by Millochau. From Meudon, in 1909, it ap- 
peared to me to cut irregularly through the lower part of the Syrtis, 




Sig 39 The half-tone Arena, in Syrtis Major, on 
20 September 1909 (o"»-Sj refractor) 



going from the estuary of the Astaboras to Osiridis Promontorium 
114 



(Fig 39)- Hale and Barnard photographed it during this year, and 
Danjon saw it again in 1922. 

nili pons. The Nilosyrtis is often seen to be detached from the 
Syrtis Major. The isthmus thus formed has been named the Nili 
Pons. Kaiser and Von Franzenau showed it in 1864, Boeddicker in 
188 1-2, Schiaparelli in 1886, Holden and Terby in 1888, T. E. R. 
Phillips from 1896 to 1903, Quenisset in 19 18, etc. In 1909, with the 
o m -83, I saw here a shadowy ligament, similar to Arena but much 
more difficult (Fig 39). The abrupt initial deviation of the Nilosyrtis 
toward the NE (Fig 37) must also contribute to the impression, as 
seen in small instruments, that the Syrtis is prolonged from its lower 
extension. 

deltoton sinus (S, 1 877). Beyond the Nymphaeum Promontorium, 
the great gulf of the Syrtis Major is continued by the Deltoton Sinus. 
The seventeenth-century sketches by Huygens showed this concave 
bay. Beer and Maedler, and J. Herschel in 1830, Maedler in 1841, de 
la Rue in 1856, Secchi in 1858 and 1862, Lockyer in 1862, Dawes in 
1864, Green in 1877 made Aeria markedly concave here. From 1877 
to 1890, however, Schiaparelli drew it differently; to him, Deltoton 
Sinus was formed by the meeting of (Enotria and Aeria. As his con- 
temporaries also showed the coast of Aeria more or less rectilinear, it 
is probable that a slight change has taken place here. Yet in 1905 
Ward saw a striking concavity, and this was photographed in 1907 
by Lowell and Lampland. In 1909 the great resolving power of the 
011-83 was enough for me to resolve the Deltoton Sinus into three 
arcuate, semi-circular bays (Fig 40), and these were confirmed on 
Hale's beautiful photograph of 5 October. 

This gulf is generally almost as sombre as the Syrtis, but to me it 
appeared pale in 1928-9. In 1909, with the o m -83, I saw it greenish 
(e =* 358°); in 1924 also it was green until October, but greyish- 
brown after 8 November (e = 18 ). 

typhoni sinus. The estuary of the Typhon on the Deltoton Sinus 



US 



was observed as a slight indentation by Schiaparelli in 1879, and as 
a dark spot in 1890. Other observers have also seen it. This bay cor- 
responds to the middle of the three parts of Deltoton Sinus (Fig 40). 

sinus sabjeus (S, 1 877). By this name, the Milan astronomer in- 
dicated the long, sombre gulf which extends from Hammonis Cornu 




Fig 40 Deltoton Sintis and Incurea Insula, on 
so September 1909 (o m -S3 refractor) 

to Thymiamata. To avoid confusion, however, I have kept this name 
for it only up to Flammarion's 'Meridian Bay*, henceforth named 
Sinus Meridiani. Sinus Sabjeus was first drawn by Huygens, in 1659." 
Herschel represented it several times in 1783, and Schroiter saw it 
better in 1798 and 1800. Beer and Maedler saw it in 1830 as a wavy 
ribbon or serpentine arc, convex to the N. In 1839 Galle showed the 
streak as narrow to the E and the W and broader in the middle; this 
was confirmed by Secchi twenty years later. I also confirmed this 
structure, using the o^ in 1909 (Fig 41), 1911, and from 1 921 to 
1928; this agrees with the American photographs. The N shores, 
better defined than those to the S, include the double port of Portus 
Sigeus and several lesser features, indicated by Nasmyth in 1862. It 
is noteworthy that Sinus Sabaeus has not changed sensibly during the 
past 140 years, although Schiaparelli drew it very narrow to the W in 
1879 and broad in the middle from 1881 to 1884. The doubling of the 
gulf reported by the Milan astronomer in 1890 is, I think, clearly an 
optical and unreal effect, and this is also the opinion of Cerulli. 

This area is characterised by differences of intensity. In general it 
is very dark; apparently the most intense region is the edge which 
extends from Hammonis Cornu to Portus Sigeus and sometimes in- 

116 




€ U. A 



Fig 41 Sinus Sabaus, with the lakes to the north; Sirbonis 

Palus, Semiramidis Lacus, Sphingos Laeus and Ismenius 

Lacus, on 27 November 1900 

eludes it. Generally, the colour of the Sinus is bluish-grey and very 
dark, as was recorded by Schiaparelli in 1883-4 ( e = I 4°°)'f ten vcars 
later, Maunder described it only as 'natural grey' (e = 356°) ; in 
1898-9, Molesworth saw it greenish-grey (e = ioo° to 140 ) and from 
1900 to 1903, indigo (e = 130 to 210 ); in 1900-1, Douglass found it 
a pale bluish-green (e - 150 ). In 1909 and 191 1 (e = 358° and 71 ) 
I found that Sinus Sabaeus was always blue-grey, never greenish; in 
1924, with the o m -83, I saw it as greyish cobalt-blue, dark until 
October (e = 309 to 354 ) but chocolate brown in November and 
December (e = 18 and greater); Lyot confirmed this during the 
same period. In 1926 it was first grey-blue (e = 346 °), then chestnut 
grey (e = 8° to 28 ). Lastly, in 1928, from Meudon, it appeared grey, 
very slightly greenish, in December (e = 83 °) and in 1929 grey (e = 
11 8°) with the great o m, 38 equatorial of the Paris Observatory. Thus 
the bluish-grey colour of the Sinus Sabaeus passes into brown some 
time after perihelion (e - 8°), to turn subsequently to grey very lightly 
tinted with green, and finally staying bluish-grey for a long time. 

In 1898-9 Cerulli noticed a series of small cuneiform patches in the 
Sinus, like the teeth of a saw; and in 1907 Eddie made out a patchy 
structure. 

It is rather rare for Sinus Sabaeus to be noticeably veiled. However, 
to me the yellow clouds concealed it completely in August 1909 and 
January 1925. 

117 



xisuthri regio (S, 1881-2). An island in half-tone, drawn by 
Schiaparelli in 1879 and 1881-2, along the whole length of the Sinus 
Sabaeus. We are dealing here with a real feature, exaggerated by con- 
trast effects. In 1896-7 I saw it well, with good images, and Stanley 
Williams, Phillips and Molesworth also drew it at this time. I noted 
this smoky island in 1928-9; it appears to develop after e = 6o° 

iapeti insula (S, 188 1-2). Small island to the N of Xisuthri Regio; it 
was seen from Milan in 188 1-2, and by myself with the o m -83 in 1926. 

PORTUS SIGEDS (S, 1 888). This threadlike feature of the N border of 
the Sinus Sabseus was first drawn by Galle in 1839, and its permanent 
existence was established by Terby." Secchi in 1858, Lockyer, Lassell 
and Phillips in 1862, Trouvelot in 1873 and Schiaparelli in 1877 
represented it well. In the latter year Green resolved it into two small 
bays, as did Schiaparelli in 1879. This double structure was confirmed 
by H. C. Wilson in 1892, by Lowell and Douglass since 1894, and by 
myself at Meudon in 1909 (Fig 41); it is also recognisable on the 
beautiful photographs taken in 1909 by Barnard, and on those taken 
in 1924 by Hubble with the great 2 m> 57 Ritchey reflector at Mt 
Wilson. 

This dark patch probably changes colour at the same time as the 
Sinus Sabaeus. 

It was less veiled than the Sinus at the time of the extraordinary 
pallor of August 1909. 

sinus meridiani. I have given this name to the 'Meridian Bay', 
also named the 'Forked Bay', and chosen by Msedler as the zero point 
for areographic longitudes. It is almost as large as France. J. D. 
Cassini was the first to draw it, in 1666 (Fig 42), and Herschel re- 
presented it in 1783. Schrceter often saw the Sinus Meridiani between 
1785 and 1802; and on 31 July 1798 he showed it basically square, 
with two points extending to the N— the first indication of its double 
structure. This irregularly quadrangular aspect was subsequently con- 
firmed by Kunowsky in 182 1-2. With their o m -i09, Beer and Midler 

US 



showed the Sinus as round in 1830, which Maunder has justifiably 
attributed to the inadequacy of their telescope; but their o m -24 showed 







Fig 42 Sinus Meridiani and Mare Acidalium joined by 

the Gehon, according to J. D. Cassini in 1666 (o m -o6i 

refractor) 

the Sinus as rather square in 1839. In the same year Galle made a better 
drawing of it; not only did he show the bay as almost quadrilateral, 
but he made it broad to the S, extended toward the SW and inclined 
toward the NE, giving him the impression of a 'duck's head' with 
Margaritifer Sinus on 14 March. 15 On 20 and 22 September and 27 
October 1862, Lassell represented it as clearly forked. In 1865, more 
than two years after the publication of LasselPs observation, Dawes 
claimed priority (as with the dusky ring of Saturn); he stated that he 
had discovered the double nature of the bay on 22 September 1862. 
Then, on 31 October 1862, Kaiser saw the doubling of the feature. 
Thus Dawes was neither the first to see it, nor to name it the Forked 
Bay. I momentarily glimpsed the double bay in 1892 with an o m -io8 
reflector when Mars had an apparent diameter of 24*. This corres- 
ponds to an analogous observation made by Schiaparelli in 18S6 with 
his o m -2i8 refractor on a 12"- 3 disk. On 19 February 1929, Giacobini 
and I saw the doubling of the Sinus Meridiani clearly from the Paris 
Observatory, using the great o™^ equatorial at the East Tower when 
Mars subtended a disk of 9"- 8. Then, on 30 March 1929, I was still 
able to see the doubling with the Meudon refractor on a disk of only 
7". Dawes drew the two points of the gulf too close together, and also 
exaggerated their inclination ; he gave an angle of 55° with the meridian 
compared with the 15 found by Schiaparelli. Green and Knobel later 

119 



made the inclination 45 and 50 respectively. My results at Meudon 
confirm those of the Milan astronomer on this point, and show a broad 
bay— a view made possible by the reduced diffraction with the great 
objective. In 188 1-2 Schiaparelli, with his keen eyesight, saw the 
points of the bay converge somewhat According to my latest data, 
the E bank of the gulf first runs down parallel to the meridian and 
then veers toward the NE. This point seemed the longer of the two 
to Schiaparelli from 1879 to 1882, although Baiddicker noted the 
contrary in the latter year. In 1924, from Meudon, I found that the 
left-hand point was the longer; it was also the darker, and was very 
slender (Fig 43). These observations were confirmed by Hubble's 
photograph with the 2^-57 reflector. Barnard and Schiaparelli in 1892, 
and Ward in 1905, saw the points shifted well to the N, though I 
noted the contrary from 1909 to 1928. We must take perspective into 
account here; the horns appear shortened when at the centre of the 
disk. Kaiser showed the exterior as ragged and the interior as mottled ; 
this was confirmed by Schiaparelli in 1 881-2 and by myself in 1924. 



3ao 33o 340 35o 







Pig 43 Chart of the Sinus Sabeeus and Sinus Meridiani in 1924 (o">-5j refractor) 



120 






The E point appeared to border a dark circular spot to Douglass in 
1898-9. Finally, Schiaparelli believed that the two points sometimes 
show a change in direction, though proof is lacking. 

Maunder has found that the Sinus Meridiani has not changed 
since 1862; this is also my impression. 

This strange bay, which is crossed by the equator, has struck all 
areographers by its sombre colour; only the Agathodsemon and the 
blackish lakes around Thaumasia are unquestionably darker. The 
Lacus Hyperboreus and the Mare Acidalium can sometimes be darker 
than the Sinus Meridiani; but their intrinsic intensity is probably not 
so dark, because it is enhanced by the snow covering of the neighbour- 
ing lands. More than once Schrceter saw the Sinus Meridiani isolated, 
without a trace of the ribbon to the left joining it to the other dark 
areas. The shading here is not uniform, being most obvious on the 
points and to the S of each of them, leaving in the middle a half-tone 
and a bright strip which emerges at Aryn and is directed upward. 
This object cannot be seen without a large aperture; it is shown on 
Schiaparelli's drawings of 1890, and those of Lowell and Douglass 
made since 1894. G. Fournier has seen it since 1909, and so have I 
in 1924 (Fig 43), 1926 and 1928. Others have also observed it. The 
photographs taken by Barnard in 1909, and that by Hubble in 1924, 
show this smoky isthmus quite clearly. It must therefore be regarded 
as a permanent feature. The estimates of the colour of the Sinus 
Meridiani are interesting. Bceddicker saw the bay as blue from 1881 
to 1884 (e = 93 to 154°); Schiaparelli grey in 1888 (e = 227 ). From 
Meudon, in 1909 and 191 1, I distinguished a dark bluish-grey (e = 
358 to 71 ); in 1920, Brindley saw it as blue (e = 212 ); in 1924 I 
was struck by the bluish -grey dark cobalt of the Sinus until the end of 
October (e = 354°), but it became chocolate brown in November and 
December (e = 18 to 36 ). In 1926 I at first distinguished a bluish- 
grey (e = 346°), then grey-brown (c - 8° to 28 ). In 1928 (e - 83 ) 
I first saw a light greenish-grey with the o m '38 at the Paris Observatory, 
and then cobalt blue on the 7*-o disk (e = 135 ). It seems, then, that 
the Sinus Meridiani, like the Sinus Sabasus, is generally dark blue, 
passing into brown after perihelion and later to grey. 

121 



At the time of the great pallor of August 1909, the Sinus Meridian! 
was practically hidden, and from Juvisy it appeared the ghost of itself 
And in January 1925 it was hidden by yellow clouds as seen on the 
7 # "5 disk with the great Mcudon refractor. Finally, it was again veiled 
at the beginning of February 1927. 

dbpressio olympiad This is the dark mass above the E horn of the 
Sinus Meridiani. From 1894 to 1907 Lowell observed his oasis 'Olym- 
pia* in this position. 

daphnes depressio. Another dark mass, above theW horn of the 
Sinus Meridiani. Lowell noted it from 1894 to 1897, calling it 'Daphne'. 

amenthes (S, 1877). Continental region, limited by the Lethe and 
the Triton to the S, the Thoth I to the W, the Eunostos II to the N 
and the .tfthiops to the E. In ,S 77 Schiaparelli found it brighter than 
Libya or Hcspcna; in 1879 it was shaded between the Lethe and the 
/Ethiops. In 1898-9 Cerulli observed it as smoky, It again appeared 
bright to me in 1909 and 191 r, and also at the start of my observations 
in 1924, but it began to darken from 3 August (e = 31 8°). Thus the 
surface here varies, becoming grey rapidly and in a marked manner. 




Fig 44 Nix Hesperia, on 13 November 1911 
(om.gj refractor) 

Secchi found Amenthes red, and speckled with brilliant points- Brcd- 
dicker called it orange-red. In 1924 it was rose-red before the darkening 
which came in August; at the end of October I saw a striking carmine 
tint (e - 2 ). 6 

This land sometimes whitens when observed under oblique light- 




ing; this is shown by the observations made by Schiaparelli in 1888, 
myself in 1898-9, Eddie in 1907, and myself again in 191 1, from 
Meudon. 

nix hesperia. A whitish area is sometimes seen on Amenthes, of 
variable extent and appearance, lying to the N of Hesperia and the 
point of the Mare Cimmerium. Thus in 1871 Webb and Gledhill 
observed a white patch here, 19 seen similarly by Burton in 1882. 
Eddie noticed it several times in 1907, and at the same time Nangle 
saw it accompanied by a smaller patch to the NE. In 191 1, with the 
o m -83, I saw it in the guise of a surface whitening about 4 in extent, 
presenting an 'unpolished' surface of uneven brightness (Fig 44). It 
seems probable, therefore, that Nix Hesperia is a permanent feature. 

libya (S, 1877). Limited by the Mare Tyrrhenum to the S, the 
Syrtis Major to the W, the Nepenthes to the N and the Triton to the 
E, this tropical land is very blunted to the S, as was shown on Huy- 
gens* sketches. Herschel, Schroeter, Flaugergues and Arago showed its 
arcuate form; Libya has been drawn in this shape almost constantly 
ever since (Fig 45). Moreover, Hale's 1909 photographs show three 
blunt capes here, separated by a slightly pointed bay. In 1928-9, with 
the o m -83, I saw that Libya was very broad and developed to the S. 




Fig 45 Libya shaded and Mceris Lacus 
enormous, on 20 September igog {0^-83 refractor). 

The encroachments and retreats of the Syrtis Major upon Libya 
have been described above. 



122 



123 



Libya varies in intensity. Normally it is very strongly shaded, par- 
ticularly to the W. The grcyness was indicated as early as 1802 by 
Schratcr, and it has since been seen by numerous observers. In 
general, Libya was smoky from 1841 to 1890, bright from 1892 to 
1907, and has been strongly shaded ever since 1909. These changes 
do not seem to be in any way seasonal. Schiaparelli saw Libya pale 
yellow in 1877; grey to the right, red to the left in 1879; then red a 
lLttle darker, from 1881 to 1886. The W coast seemed to him to 'be 
even darker in 1883-4. Holden and Kecler later noted it as red in 
1888; Niesten orange-yellow, Schiaparelli brown in 1890. In 1896-7 
Cerulli made it orange-red, while I made it brick-red. From 1909 to 
191 1, with the o»-8 3 , I could see only violet-grey, with no redness; 
in 1924 it again seemed to me to be brick-red. It was strongly smoky 
in 1926; the colour was dull red on 14 September, violet on 18 and 
19 October. In 1929 Libya appeared ochre, with a greyish cast. 

A curious structure was noted on Libya by Schiaparelli. In 188 1-2 
he wrote to me: 'The surface shows the aspect of a hairy tissue, or. if 
you hke, gives the impression of being full of tiny holes,'" In 1883-4 
it seemed to have a 'flaky texture'. 18 

Libya sometimes appears brilliant, covered with clouds. One of the 
best cases was that of 29 July 1907, observed by Jarry-Desloges in 
France and by Eddie in Cape Colony; Libya appeared very brilliant 
when near the central meridian. It is unusual for an opposition— even 
a penhehc one-to pass without Libya sometimes being seen as 
whitish or white at the edge of the disk. On 11 October 19,1, from 
Meudon, I found that after sunrise over it, it was covered by numerous 
white tufts, narrowing because of perspective effects and being dis- 
placed toward the SE-forming a vast cloudy cloth which, on the 
14th, covered the adjacent seas. 19 

osiridis promontorium (S, 1877). The NW point of Libya was 
observed by Schiaparelli, in 1877, as a long peninsula, blunted at the end 
(Fig 46); but in 1879 it seemed to him to be truncated. In igoq 
with the om-83 , it was clearly sharp. 

124 



MCRRis LACUS (S, 1 877). An enormous lake spreads out to the N of 
Libya; its surface area is almost as great as that of the Black Sea, It is 
not very dark, and appears to be variable. 20 It was first drawn by 
Mfi'dlcr in 1841, as part of a gulf of the Syrtis Major. It was shown as 
fairly large by Secchi in 1858, by Lockyer and by Lord Rossc's 
assistant in 1862, by Kaiser and Dawes in 1864, by Flammarion and 
Green in 1873, by Green in 1877, by Burton in 1879, by Beeddickcr 
in 1S81-2, by Trouvelot in 1884, by Flammarion in 1890, by Ilussey 
and Eddie in 1892, by Campbell in 1894, and by myself at Meudon 
from 1909 to 1928. Its great extent in 1909, to which I drew attention, 21 
was confirmed on the photographs taken by Hale, Barnard and Lowell. 
At other times, however, the lake may be invisible, forming a gulf in 
the Syrtis Major. This aspect was seen by, among others, I lolden in 
1875, Lowell between 1894 and 1907, the Abbe" Morcux in 1896-7, 
Millochau, Douglass and myself in 1900-1 Millochau in 1903, Ward 
in 1905, and on the beautiful photographs taken by Lowell and 
Lampland in 1907. 

With perfect images with the o m *83 on 20 September 1909, I saw 
the Lacus Mceris as truly vast, elongated in an E-W direction, ir- 
regularly elliptical, and containing a peninsula and an island which 
were constantly visible (Fig 45). Using the o m -83 I again saw this 
structure on various occasions up to 1928. 

It is strange that Schiaparelli, who noted the lake as black in 1877, 
1881-2 and 1890, never saw it as large as it really is, although many 
of his contemporaries drew it the correct size. Flammarion in 1873, 
with an o nu io8 telescope and a 13" disk, described it accurately; but 
normally the Moeris Lacus shows as a half-tone. I saw it extended in 
1927, with the o m -83, on an 8"-o disk. 

Cerulli found the Mceris Lacus strongly reddish in 1898-9 (e = 
138 ). In 1909 (e = 358°) and 1924 (e = 338 ) it seemed olive to me 
from Meudon. 

Light cloud is sufficient to conceal this lake. 

cyllexius lacl:s (S, 1890), This object lies on the Triton, between 
the Mare Cimmerium and Tritonis Lacus. Noticed by Schiaparelli in 



125 



1890, it seemed to me in 1909, using the o"-83, to be irregularly ex- 
tended in the same way as the Triton (Fig 62). Its colour was then 
greenish indigo. 

libyc/e paludes. These arc two small lakes to the NW of the Cyl- 
lcmus Lacus; I saw them from Meudon in 1909 (Fig 62). That to the 
left k comparable with Lake Pcfpous; that to the right, glimpsed for 
the fract.on of a second with the o™-8 3 , is very small, but still larger 
than our Lake Geneva. 

TRiTONis lacus <S, 1877). Observed by Cruls and also by Schiapa- 
relli, in 1877, to the NE of the Lacus Mceris,* and described by 
Schiaparelli as quite easy, oblong from N to S (Fig 46). This interest- 
ing lake was again seen from Milan in 1879. However, it showed up 
only as slight broadening of the Thoth I in 188 1-2, when Schiaparelli 
and Burton stated that a white spot occupied the major part of this 
object." It was not seen from Milan in 1883-4; but from 1886 to 
1890 the Italian astronomer drew it almost as he had done before. 
Lacus Tritonis was also shown by Gmllaume in 1890 and by Hussey 
in 1894, when it appeared elongated in an E-W direction. Stanley 
Williams in .894, Cerulli in 1898, Millochau in 1903 again observed 
it. I did not see it from Meudon in 1909, 1911 (Figs 45 and 37), 1924, 
1926 or 1928, when it seemed to be a part of the x\'epenthes-clon- 
gated along the meridian, fragmented and restricted. 

isidis regio (S, 1877). Limited by the Nepenthes to the S, the 
Syrtis Major and the Nilosyrtis to the W, the Astapus to the N and 
the Thoth I to the E, this region shows changes of extent on its right- 
hand side at the same time as Libya-due to alterations in the Syrtis. 
It seems also to be variable in intensity. As early as 1802, Schroeter 
showed it as smoky. After a long period during which it was apparently 
bright, it again became shaded; Kaiser in 1862 and 1864, Trouvelot 

• 'The Lake of Triton,' wrote Schiaparelli, 'was very well seen by Mffidler as earlv 
126 



in 1873, Niesten in 1879 and 1881-2, Bceddicker in 1881-2 and Miss 
Everett in 1892 all represented it as a half-tone. From Meudon, in 
191 1, it appeared very smoky (Fig 63). Quenisset drew it greyish in 
1918, as did Danjon in 1922. 1 saw it similarly in 1924, 1926 and 1928, 
when, however, its intensity did not always appear the same. Isidis 
Regio is variable in colour. It appeared red to Secchi in 1856 (e =- 
203 °), orange- red in 1858 (e = 250 ). Holden and Kceler saw it red 
in 1888 (e = 255"). With the o m -83, in 1911,1 could see only a greyish- 
violet tint, with no trace of red (e = 56 ); in 1924 I found it smoky red 
(e - 338 ); in 1926 it was grey (c = n" to 32 ) and in 1928, shaded 
reddish (e - 86°). 

Secchi saw a mottled structure here in 1858. 

Isidis Regio is often covered with whitish clouds. Schiaparelli was 
struck by its brilliance in 1877; he again noted the remarkable bright- 
ness in 1 88 1 -2 and from 1886 to 1890. I saw it sometimes brilliant 
when near the centre of the disk in 1896-7 and 1926-7. These effects 
are due to atmospheric veilings. The white tufts seen from Meudon 
on Libya, in 191 1, also covered Isidis Regio. It is often seen white 
under oblique lighting, as was noted by Schiaparelli in 1877; and it 
can sometimes appear brilliant even when on the edge of the 
disk. 

nix atlantica (S, 1877). 'A small part of the Region of Isis,' wrote 
Schiaparelli in 1877 (indicated on his map by a pointed contour im- 
mediately W of the Lake of Triton), 'showed up on 14 September as 
more brilliant than any other part of the planet. I do not hesitate to com- 
pare it with the polar snow. I again saw this white spot very distinctly 
on 14 October; to me it formed a white square with a side 1-5 degrees 
long— so that the full circle was nearly 8°. 23 In 1879-80 the Milan 
astronomer rcobserved this interesting spot 'on 7 and 8 December, 
and again with absolute certainty on 9 and 10 January; it seems there- 
fore to be very persistent, and even if it is not permanent it certainly 
reappears at set intervals. It is easy to suppose that it is due to snow 
spilling over from the very cold neighbouring region, and this is why 
it is named Atlantic Snow on my map.' 24 At this time, the form 'had 



127 







Fig 46—1877 Fig 47—1879 Fig 48—1881-82 
Observations of Nix Atlanlka by Schiaparelli (o»*-2i8 refractor) 



\ 

Tl4 ! 



become a little less round'." Schiaparelli saw it again, for the last time, 
in 1881-2. 'It was again visible during the whole of the opposition,' 
he wrote. It then appeared elliptical, elongated in a N-S direction. 
'With regard to its brilliancy, the variations have not ceased, and it has 
not always been easy to judge whether they are real or whether they 
are due to differences in the conditions under which the observations 
were made.' 29 It seemed to be a little feebler until December 188 1, but 
in 1882 'it had become brilliant by the time the Sun was exactly at its 
zenith'." Figs 46 to 48 show the various aspects of the patch as 
Schiaparelli recorded them with his o m -2i8 refractor. 

'If its appearance depends on the period of the Martian seasons,' 
wrote Schiaparelli in 1888, 'we should have to wait until the opposi- 
tions of 1892 to 1897 before seeing it again. Its reappearance will be 
important in studies of the physical constitution of the planet.' 28 

On 13 March 1882 Burton confirmed the existence of Nix Atlantica, 
but it did not seem to him to be very obvious. 48 

According to Schiaparelli, the position of the white patch is about 
long 268°, lat + 1 8°. Burton's observation gives long 26 1°, lat + 21 . 
From Milan, in 1 881-2, the region to the W of Nix Atlantica ap- 
peared very white. It was here that Gledhill and Molesworth, in 
1898, noticed a small, circular, brilliant patch a dozen degrees west of 
the patch observed by Schiaparelli. This second object was con- 
firmed in the new position by Eddie in 1907 and by Phillips in 1909, 
when it was also photographed by Hale (Fig 36). I saw this patch 
very easily in 191 1 with the Meudon refractor, when its shape was 
slightly oval, pointed to the,SW; in colour it was dull and irregularly 

128 






white (Fig 63). Graff also saw it like this, and Phillips again noted it in 
1 91 8. I recovered it in 1924, and less well in 1926 and 1928 with some- 
what unsteady images lacking in detail. We have here one of the 
curious features so characteristic of the region. 

The question which naturally comes to mind is: Is this new bright 
spot identical with Schiaparelli's? The probable answer is 'No', 
because in 1877 the snow appeared too far from Syrtis Major for it 
to be the same as the snow of 1898, which lay very close to the Syrtis. 
This objection is supported by the still more easterly position of 
Burton's spot, and also by the whiteness which I glimpsed in 1928 
in the position given by Schiaparelli. On my map, the new white spot 
is 12° to the W of the famous Nix Atlantica of the Italian astronomer. 

neith regio (S, 188 1-2). This land was originally bounded by the 
Astapus to the S, the Nilosyrtis to the W, the Borcosyrtis to the N 
and the Casius to the E. I have detached the lower shaded area so as 
to make it bounded by the Asclepius. It is darkish, particularly under 
the Nasamon, where the greyness — which is sometimes intense, and 
forms a reversed V — completes the 'hour-glass' of the Syrtis Major. 
On his sketch made in 1777, Herschcl showed the shading of Neith 
Regio; this was the first time that it had been drawn. It has since been 
shown on drawings by numerous other observers, and it was photo- 
graphed by Lowell and Lampland in 1905. To me, Neith Regio ap- 
peard smoky from 1898 to 1903 (Fig 37) and in 1916. Both Secchi and 
Holdcn described it as red. 

Schiaparelli saw Neith Regio white near the edge of the disk in 
1888, and others have confirmed this since. 

umbra. This is the smokiest, NW part of Neith Regio. It was seen 
as very strongly grey by Herschel as early as 1777 and 1779, and by 
other observers since, including Moreux and myself in 1S96—7. 
Lampland's photographs of 1905 show a fairly dark half-tone here; I 
saw it in 1903 (Fig 32), 191 1 and 1916, 

nodus alcyoxius (S, 1890). This remarkable lake, larger than our 

129 



Lake Superior, lies to the SE of the Casius, almost 1,000km to the 
north of Triton is Lacus. Beer and Midler observed it in 1830, 1837 
and 1 841. Many other areographers have drawn it since. It is an easy 
object, almost 6° broad, and very sombre— sometimes blackish. 




Fig 40 The region of Syrtis Minor, showing at the 

base Nodus Alcyonius and Utopia looking dark, on 

7 June /90J (0™-2i6 refractor) 

Sccchi showed it intense in 1856, feeble in 1858; Holden drew it well 
in 1879. It was not well-defined to Schiaparelli in 1879, but it ap- 
peared to him as a black right-angled feature in 188 1-2 (Fig 58), 
though less dark at following oppositions. In 1S96-7 it was again seen 
as sombre, this time by Cerulli and myself, and I also saw it as intense, 
from Paris, in 1903 (Fig 59) and 1905 (Fig 49). It was the same as' 
seen from Meudon in 1911 (Fig 63) and in 1915-16. Finally, G. 
Fournter and Thomson in 1913-14, Briault from 1916 to 1918, Mme 
G.-C. Flammarion in 1918, and myself in 1926 all observed it as 
blackish. As with many other patches, the Nodus Alcyonius emerges 
dark from winter, and becomes paler under the increased solar radia- 
tion as the Martian seasons draw on. With the Meudon refractor I 
saw it excellently in 1927, with a magnification of 1250 on a 7*7 disk. 
In 1879, Schiaparelli found the lake greyish -azure or bluish. 
Naturally, local clouds sometimes make this remarkable object look 
pale. They may even conceal it. 

utopia (S, 1881-2). This second dark lake, occupying the area 
between the Alcyonius and the Casius to the S and the Hcliconius to 
the N, was called 'Alcyonius Sinus' by Schiaparelli in 1879. It is 
shown on a sketch made by Hooke as early as 1666, and also on a 

130 



drawing made by Huygens in 1683. 30 Herschcl in 1777 and Schroeter 
in 1785 showed it blackish. Later, Beer and Maedler, and also Gallc, 
drew it as very dark in 1839; Masdler very sombre in 1841, Secchi 
intense in 1858. Gledhill and Burton found it rather feeble in 1871; 
Flammarion, Schmidt, Burton, Green and Lohsc dark in 1873. 
Terby noted it as intense on one occasion in 1875, as did Bccd dicker 
in 1881-2. Trouvelot, Boed dicker and Lohsesaw it blackish in 1883-4, 
as did Denning, Niesten, Keeler and Holden in 1888; Gledhill and I 
saw it even more sombre in 1898-9, and so did Milloehau in 1900-1. 
I noted it dark in 1903 (Fig 59), and it was the same to Ward in 1905 
and Eddie in 1907. I again observed it as intense in 191 1 and 1916, 
and so did Briault in 1918 and Quenisset in 1918-22. Finally, it 
appeared dark once to me in 1924 and quite sombre in 1928. 

It is curious that Schiaparelli should never have shown as dark on 
his maps an area which had been seen by Hooke, Huygens and other 
observers! But Schiaparelli used very powerful eyepieces, and often 
employed a magnification of 690 on his o ra -2i8. 

It seems that Utopia is at its darkest in northern spring. 

Schiaparelli saw a green tint here, Le Coultre a bluish-grey or 
blackish hue. 

Milloehau and Lowell noted a patchy structure on Utopia in 1903. 

In 1898-9, Cerulli and I found that Utopia seemed darkest when 
near the edge of the disk. 

Atmospheric veiling sometimes makes this patch look pale. It was 
white in December 1924, according to my observations with the 
o m -83. 

HOTRODi FONS. This is the lake on Utopia observed by Lowell in 
1903 and 1905, and called by him 'Botrodus'. 

oniri fons. A small lake, seen by Molesworth on the Casius in 
1900-1. I reobscrved it in 1903. 

asclepii PONS. Isthmus on the Boreosyrtis, observed by Schiaparelli 
in 1 881-2 (Fig 58). 



131 



nili lacus. A light enlargement of the Nilosyrtis at its extreme 
E end. In 1858 Secchi drew a projection from the main strip in this 
position, confirmed by Trouvelot in 1873, Bccddtcker in 188 1-2, and 
Cerulli and Douglass in 1898-9. Lowell observed the Nili Lacus from 
1903 to 1907, and called it 'Nilus Lucus". G. Foumier noted it in 
1913-14 and in 1920, Briault in 1918. In 1911 it seemed to me to be 
a broadening of the Nilosyrtis (Fig 37). 

boreus pons. In 1873, Trouvelot drew a break between the Nilo- 
syrtis and the Boreosyrtis. It was often shown by Schiaparelli from 
1881 (Fig 58) to 1890. As Niesten and Flammarion also showed this 
isthmus in 1888, it is presumably a permanent feature. 

meroe insula (S, 1 879). According to Schiaparelli, the Nilosyrtis 
and the Astusapes together form an elongated and almond-shaped 
island. It is shaded, particularly to the S, as is shown on the sketches of 
Beer and Masdler in 1832, Schiaparelli in 1890 (Fig 66) and myself 
in 191 1 (Fig 37) and 1924. Lowell and Lampland photographed this 
island in 1907; it was then completely shaded, particularly in the S. 
To me it seemed smoky in 191 1, less so in 1924 and 1926. Le Coultre 
observed it as orange in 19 16. 

In 1858 Secchi was struck by the many small white streaks here. 
Schiaparelli noted one of them in 1881-2, and in 191 1 I saw two, of 
which the southern was the larger (Fig 37). 





■ 



Fig 5° Coloe Palm, Protottilus and Ismenius 
Lacus, according to Trouvelot, on 1873 (o m -38 refractor) 



132 



Meroe was noted as white near the limb in 1886 and 1888 from 
Milan, and other observers have since seen the same appearance. 

coloe PALUS (S, 1879). This lake, at the W extremity of the Nilo- 
syrtis, is roundish, though somewhat irregular; it is 300km across, 
comparable with our Sea of Aral, Beer and Maedler drew it in 1839 
and 1 841. It was well shown on a drawing by de La Rue made in 
1856, but Secchi, two years later, did not record it at all. In 1873, to 
Trouvelot (Fig 50) and Green, Coloe Palus seemed enormous; at this 
time Terby saw it with an o m -io8 refractor! Holdcn in 1875, Schiapa- 
relli in 1879, and Boeddicker and Niesten in 188 1-2 showed it extended. 
It was not seen from Milan from 188 1 to 1886, and though Niesten 
drew it dark and elongated in 1888 the Italian astronomer saw only 
two parallel tracks — clearly optical in nature. In 1890 Keeler showed 
the Coloe Palus as large and obvious, and to Guillaume and Schiapa- 
relli it seemed considerably extended (Fig 66). I observed it in 1896-7, 
1900-1 and 1903 (Fig 32), and Millochau also showed it. Vast to Ward 
in 1903, it appeared superb to me in 1909, with the o m -83; it showed 
up as an ellipse, grey near its border. In 191 1 I was astonished by the 
case with which it was seen from Meudon (Fig 37). G. Fournier 
drew it large in 1913—14, Briault also in 19 15— 16. However, Briault 
showed it as small in 1918; Quenisset made it more extended. It was 
still striking in 1927, when I saw it well on an 8" disk with the o m -83, 
and I again noted it as extended in 192S. Ellison saw it blue in 1918 
and 1920. 

It seems, then, that the Coloe Palus is not always visible. The varia- 
tions are partly due to yellow clouds which sometimes hide it. 

pseboas lacus (S, 1 883-4). This is probably another lake, much 
smaller than Coloe Palus, drawn by Schiaparelli in 1881-2 31 and also 
m 1SS3-4; but in 1886 and thereafter the Milan astronomer did not 
reobserve it, despite his using an o m '49 refractor. However, Millochau 
showed a small dark spot here in 1 900-1. 

nili portus. A small harbour on the S bank of the Nilosyrtis, to 

133 




Fig Si 



Ismenius Laeus, Arethusa Lacus, and the Mare Acidalium, 
observed on 15 January iqot (0*1-240 refractor) 



134 



the E of Coloe Palus. It was drawn by Trouvelot in 1873 (Fig 50) 
and confirmed by Schiaparelli in 188 1-2 and 1890 (Fig 66). 

astabor.^ fons. In 1 88 1 -2 the Milan observer noted another 
small lake, at the intersection of the Phison I and the Astaborus. It 
appeared double to him in 1890. It was confirmed by Ccrullj in 1898-9, 
by Millochau, Denning and Lowell in 1903, by G, Fourhier in 1909 
and 1911, and by myself at Meudon in 191 1 (Fig 37) and 1926, when 
it appeared almost blackish, with a diameter of around 90km, 

ismenius lacus (S, 1881-2). We come now to a magnificent lake, 
situated near latitude 40 N. Kunowsky— an excellent observer— was 
the first to draw it, in 1821-2, when it appeared as a dark oblong spot 
on the Protonilus, twice as extensive as our Lake of Aral. It was 
named by Schiaparelli. It is situated in the north temperate regions, 
antipodal to the Mare Sircnum, at 2,700km from the shore of the 
Sinus Saba:us, and in the middle of the red deserts which extend on 
all sides of it. In 1837 and 1841 Beer and Maedler represented Ismenius 
Lacus as a simple broadening of the Protonilus, but in 1839 they showed 
it as broad and oval. Dawes never drew it, although he used a tele- 
scope with an aperture double that of Kunowsky. In 1856 de La Rue 
observed it as small and sombre; then, Schmidt drew it in 1858, 
Kaiser in 1864, Gledhill in 1871 and Schmidt in 1873. It was excel- 
lently drawn by Trouvelot in 1873 (Fig 50). Ismenius Lacus was again 
observed by Holden in 1875, and Schiaparelli noted it for the first 
time in 1879. The Italian astronomer saw an optical doubling of the 






lake in 188 1-2, in the form of two ovals elongated parallel to the 
equator, while Bceddicker drew them in a guitar-shaped form lying 
along the parallel of latitude — an aspect which Schiaparelli confirmed 
in 1884. At this time the lake was large, clearly elongated E-W, well- 
defined, and sombre as seen from Milan. In 1886 Schaparelli saw it 
as a large black spot, very obvious, confused, rather elongated in a 
N-S direction and with a length of io°; Celoria confirmed this aspect 
at the same time. In 1888 Ismenius Lacus appeared very large as 
seen from Milan, and was made up of two more or less circular 
nuclei, rather like a double star with components separated by io°. 
The line joining their centres was inclined 15" to the WSW, and the 
whole feature was surrounded by a feeble penumbra. In 1890, 
Schiaparelli first saw the lake as 'an enormous swelling', very dark and 
obvious (Fig 66); then double as in 1888, but without an intermediate 
half-tone, the left-hand spot appearing the smaller of the two, and 
with their edges separated by i°. In 1888 Perrotin, Ilolden and Kceler 
represented the lake as being oval, and this was confirmed by Stanley 
Williams in 1890, when Giovanozzi saw Ismenius Lacus with an 
aperture of only o m -io8. Stanley Williams reobserved it in 1892. I 
saw the lake for the first time from Juvisy in 1896-7; it was then 
diffuse and pale, and I again saw it during the following oppositions 
up to 1905. With the o m -24 and o m -2i6 telescopes that I was using at 
this time I had always seen the lake as oval (Figs 32, 51 and 65). In 
1896-7, and from 1903 to 1907, Lowell drew the lake double, as 
Schiaparelli had done in 1888 and 1890. Molesworth and Phillips 
found it easy in 1898-9. Ismenius Lacus was again elongated E-W 
in 1900-1; Millochau then found it darker at the centre than to the 
edge, and in 1903 it seemed markedly elongated (Fig 55). It was 
always very dark to Attkins and Molesworth, and Gale noted an ex- 
tension of the lake toward the W. This object was well observed by 
Eddie and Dobbie in 1907. With the o m '83 refractor in 1909 and 191 1 
I saw the lake as vast, and it was the same in 1913-14 as seen with 
my o m -2i6 reflector. In 191 3-1 4 and 1920 G. Fournier confirmed 
the doubling of the round spots, as also did Briault in 1918. In 1924-5 
and 1926, I noted it as extended and oval, and in 1925 I was able to 



135 



follow it until the disk of Mars had shrunk to f-z. In 1928, with the 
o»-83, I saw it as two condensations enveloped in a lenticular penum- 
bra lying along the parallel of latitude. Finally, on rg February 1929, 
Giacobini and I, from the Paris Observatory, saw it clearly elongated 
on a 9*-8 disk. We were then using the great o" 1 ^ equatorial in the 
East Tower. 

In 1903 I showed experimentally that a greyish ellipse, subtending 
an angle the same as that of Ismenius Lacus, will tend to appear 
double— as two spots — when the observer stares at it for a long time. 

In 1888 Schiaparclli described a f displacement of Ismenius Lacus 
toward the W, but this is questionable. 

The intensity of the lake, generally considerable when it is not 
veiled by mists, can become very great; Schiaparclli, Douglass and 
I have sometimes glimpsed it as blackish (Fig 65), and Ellison noted, 
it very sombre in 1915-16. 

Keeler found its colour greenish in 1888 (e = 254 ), and Terby 
reddish (e = 2n°); Molesworth saw here 'a very dark blue indigo' in 
1903 (e m t2oo°); in 1909 and 191 1 (e = 39 to 52 ) I noted it as 
bluish or indigo in the o m -83. Ellison saw it dark blue in 1918 (e = 
175°) and 1920 (e = 212°), If the reddish tint recorded by Terby is 
genuine, it shows that the nature of the lake is the same as that of 
the majority of the sombre, changeable areas on the planet. 

ismenia. In 1821-2, Kunowsky showed Ismenius Lacus as being 
exceptionally large; and on their 1838 map Beer and Msedlcr showed 
it shaded to the SW (Fig 52). This was confirmed by them in 1839. 




'«*:'. 






Fig 5^—1837 Fig 53—1858 Fig54-10.11 

Meedler Secchi Others 

Obscurations of Ismem'a in the middle of the nineteenth century 



136 



Galle observed something similar, also in 1839; and in 1856 de La 
Rue showed a grey area bounded by a sombre streak. Two years 
later, Secchi found an extended shading, presenting an almost semi- 
circular contour to the S (Fig 53). Finally, Trouvelot, in 1873, drew 
here a half-tone prolonging the lake toward the SW. I have seen 
nothing abnormal since 1896 (Fig 54). It follows that this country is 
not an absolute desert, since it darkened over almost 40,ooosq km 
between 1837 and 1873 only to revert later to its reddish tint. I have 
given the name of Ismcnia to this changeable region. 



akethusa lacus (S, 1 883-4). This is another lake, but less important 
than Ismenius Lacus; it is comparable in size with our Lake Huron 
together with George Bay. It lies around latitude 6o° N, and is lost 
in the middle of an immense rosy wilderness more than a thousand 
kilometres to the N of Ismenius Lacus. Its distance from the Syrtis 
Major is 3,500km; from Sinus Sabseus, 4,000km. It is not so far 
from the Mare Acidalium, from which it is separated by 1,200km. It 
is 1,400km from Dirce Fons, 1,700km from Coloe Palus, 1,500km 




Fig 55 Ismenius Lacus and AretJiusa Lacus teith the Lacus Hyperboreus 
in 1903, after Miliochau (o m -$3 refractor) 

from Lacus Hyperboreus, 2,700km from Lacus Arsenius and 4,200km 
from Propontis. Kunowsky, with his o m -H7 refractor, showed it as 
a broadening of the Pierius in 182 1-2, which is very remarkable. 
Masdler did not draw it well until 1841. Then, in 1858, Secchi saw 
it as a marked broadening of the band of the Pierius. Schiaparclli 
observed it well in 1884 as a beautiful blackish patch, clearly visible, 



137 



and very much smaller than Ismenius Lacus. In 1886 it seemed to 
him to have become large, dark, very evident and smoky at the edges, 
so that resembled a smaller version of the Ismenius Lacus. This aspect 
was confirmed by Celoria. In 1888 it appeared double from Milan, 
but smaller, blackish and single in 1890 (Fig 66). Cerulli and Douglass 
saw the lake well in 1898-9, and Molesworth followed it with an 
m. 32 reflector on a disk of Mars of only 4*7. In 1900-1 Douglass and 
I saw it vaguely; Molesworth found it very distinct and similar to the 
Pimenius Lacus. Gale distinguished it in 1903 as a broadening of the 
Piserius, while Molesworth gave it a diameter of 4 and noted it is 
almost round, feebler than Ismenius Lacus and with a small companion 
almost touching it to the E. At this time Millochau drew it extended 
inclined toward the SE, and quite dark (Fig 55). In 1903 and 1905 
Lowell glimpsed it double, as Schiaparelli had done in 1888. Ward, 
in 1905, drew it in the form of a widening of the Pierius. G. Fournier 
represented it double in 1913-14, oval in 1930. It was elongated to 
Briault in 1918. Finally, with the 0^83, I saw it as small and blackish 
at the boundary of the snows in 1928. 

According to Schiaparelli, Arethusa Lacus, like Ismenius Lacus, 
showed a westerly displacement of 1 1° in 1888, but this is doubtful. 

callirhoes fons. The name given to a small lake on the Callirhoe, 
WSW of Arethusa Lacus, seen by Schiaparelli in 1890 and confirmed 
by Molesworth in 1903. 

aeria (S, 1877). A large, rose-red desert, almost half the size of 
our Sahara, but incomparably more barren. Its limits are the Sinus 
Sabaeus to the S, the Phison to the W, the Astusapcs, the Syrtis 
Major and the Deltoton Sinus to the E. Aeria is recognisable on the 
drawings made by Huygens in 1659 and 1672. It is bright and 
luminous except in the N, where it shades off near the Astaboras, as 
1 found in the 1907 photographs by Lowell and Lampland and the 
1909 photograph by Barnard. There is also a light penumbra to the 
N of the Typhon, represented by Schrceter as early as 1800. By 
contrast with the dark sea, the beaches in these regions can somc- 

138 



times show up as brilliant white. 

Beer and Msedler, Secchi, H olden, Keeler and Maunder saw Aeria 
red, Boeddicker strikingly orange, Schiaparelli yellow-orange, Cerulli 
brick red. With the o m -83 I saw it very red in 1909 and 191 1; red, 
strongly rosy, in 1924, 1926 and 1928. This latter colouring is un- 
questionable. 

Cerulli glimpsed a granulated structure here in 1896-7. 

Yellow clouds sometimes give a golden tint to Aeria. From time to 
time white spots are seen on this immense region. Thus on 24 May 
1873, Burton drew here a small, brilliant patch, which Lohse saw 
more than io° to the E on the following day; this must have been a 
mass of white clouds which was carried along by a west wind blowing 
in the neighbourhood of the equator. In 1888 Niesten noted two white 
spots here. 

Aeria often whitens when seen obliquely, as was noted by Lehar- 
delaye as early as 1871. These temporary brightenings may become 
very striking. 

On 7 and 8 December 1900, a brilliant protuberance appeared in 
the S part of Aeria, according to Douglass ; on the 8th it even seemed 
to be detached from the terminator. Very high yellow clouds, seen 
from Mcudon on 8 October 1924, seemed to make the whole region 
protrude from the sunrise terminator. 

On 19 October 1909, Le Morvan photographed, in violet light, a 
large bright patch on Aeria, 

nymph/eum promontorium. This majestic cape penetrates for some 
distance into the Syrtis Major, where it is continued by the half-tone 
of (Enotria. It is whitish, as is shown in the 1659 sketch by Huygens. 
J- Herschel in 1830, Secchi in 1858, Lockyer in 1862 and Niesten in 
1888 are others who have drawn it, but Schiaparelli never indicated 
it. However, the photographs taken by Hale and Barnard in 1909 
show it prominently; I have observed it, under good conditions, 
with the great refractor in 1909 and again in 191 1 (Figs 39 and 
37). 

The cape has been seen as whitish by Kempthorne in 1S96-7, 



139 



Lowell and Douglass in 1 900-1 and Lyot and myself in 1926, 

^ hammonis cornu (S, 1 877). This well-marked promontory at the 
S of Aeria is recognisable on Huygens* sketch. Herschel represented 
it quite well in 1783, Beer and Maedler better in 1830. Secchi drew 
it blunted in 1858, as did Schiaparelli later. In 1877 Green showed it 
strongly curved back, and it is in this parrot's-beak form that it 
appeared to me from Meudon in 1909 (Fig 40). 

pharos insula (S, 1881-2). In 1881-2 Hammonis Cornu was 
observed from Milan to be separated from the continent by a dark 
Hne (Fig 58). The island thus formed has been named Fharos Insula. 

sirbonis palus (S, 1879). This is a small dark island, isolated in the 
interior of Aeria at about 1,200km to the NW of Hammonis Cornu. 
It has the area, though not the form, of our Lake Nyassa. Seen as 
very large and smoky in 1873 by Schmidt, it was difficult to Schiapa- 
relli in 1877. In 1879 Terby drew it as a large, billowy bog; to 
Schiaparelli it was small. Denning saw it sombre in 1886, and from 
Milan in 1888 the lake was seen double, as two round patches. Holden 
then saw it as diffuse. In 1894 Stanley Williams saw it as small. I 
noted it in 1896-7, and Cerulli and I saw it as rather restricted in size 
in 1898-9. It was small and pale from Meudon in 1909 (Fig 41) and 
191 1, according to the Fournicr brothers; but in 1924 I once glimpsed 
it as blackish, although of restricted dimensions. I saw it again in 
1926 and 1928. It is possible that Sirbonis Palus used to be larger 
than it is now, but in its modern form it is no larger than our Lake 
Ladoga, 

edom (S, 1881-2). This tropical desert extends to the right of the 
wilderness of Aeria, and is equally sterile. The name Edom was given 
to it only in 1881-2; in 1877 this land had made up part of Arabia, and 
in 1879 part of Eden. It is bounded to the S by the Sinus Sabjeus, to 
the W by the Sinus Mcridiani, to the N by the Hiddekel and to the 
E by the Euphrates; but I have detached the northern, most shaded 

140 



part of it. Edom is very distinct to the S — as much so as Aeria. It 
appeared red to Beer and Maedler and to Secchi, reddish to Glcdhill. 
In 1909 and 191 1, with the o m -83, I saw it red; but in 1924, 1926 and 
1928 it appeared a lovely, strong rose colour. 

As with Aeria, yellow clouds over Edom sometimes gild it. From 
1879 to 1882 Schiaparelli observed here a whitish streak coming 
from Dioscuria and Arabia; this was confirmed by Bceddicker in 
1 88 1 -2. Edom, also, often whitens when seen obliquely, as was noted 
from Milan in 1883-4. 

On 23 August 1894, at Juvisy, I observed a bright projection from 
the terminator at Edom. 

moab. This is the N part of Edom. In 1 877 those great observers the 
Henry brothers saw it lightly shaded beyond the Orontes; this was 
noted by others later, and I confirmed it from Meudon from 1909 to 
1928. However, this half-tone is a very delicate shading in these rose- 
red regions. 

edom fromontorium (S, 1 88 1-2). The SW part of Edom, border- 
ing the Sinus Meridiani, forms a rounded cape which seems to push 
back the Sinus Sabzeus in this area (Fig 43). Broadly and roughly 
drawn by Herschel in 1783, and by Beer and Maedler from 1830 to 
1 841, it was well represented by Kaiser in 1862, and by others later. 

This beautiful cape often appears bright. In September 1896 
Cerulli saw it, near the terminator, as white as snow; this was con- 
firmed at the same time by Molesworth, Phillips and Kempthornc. 
Phillips has seen it white at almost all oppositions since 1896. To me, 
it appeared whitish in 1926 and 1928. 

fastigium aryn (S, 1877). This very striking promontory, formed 
by the fork of the Sinus Meridiani and whose tip marks the zero 
point for Martian longitudes, is not sharply defined on Schrceter's 
drawings. Galle showed it similarly in 1839, and Lasscll sketched it 
clearly in 1862; but Dawes represented it as much too narrow in 1864, 
It was shown more accurately by Schiaparelli in 1877. From Meudon, 



141 



I always see Aryn as part of the head of a parabola, inclined to the 
meridian by about 15 (Fig 43). 

Kaiser drew this cape as shaded in 1862; this was confirmed by 
Schiaparelli in 188^2 and by myself at Juvisy in 1896-7. From 1900 
to 1903 Millochau failed to show this greyness, but with the same 
telescope I glimpsed it at the end of 1909. I have particularly noted 
that the albedo, which is exactly the same as that of Eden, is inferior 
to that of Edom and the region S, of Thymiamata. This half-tone was 
also noted by the Fournier brothers from rgog to 1914 and by Briault 
from 1915 to 1918. 

semiramidis lacus. Small lake, seen in 1890 by Schiaparelli on the 
Euphrates at its intersection with the Orontes. CeruIIi observed it in 
1989-9, Douglass in 1900-1, Denning in 1903, Lowell in rgoy. G 
Fournier drew it in 1909 and 191 1, and in 1909, from Meudon, I 
glimpsed it as small and blackish (Fig 41); I also saw it in 1924, 1926 
and 1928. Its surface area is greater than that of Lake Onega. 

euphratis LACUS. This is another lake, noted by Schiaparelli in 
1890, lying further to the N of the Euphrates, Cerulli saw it again 
from 1896 to 1899, as did Lowell in 1907, Briault in 1915-16, and 
myself in 1928. 

Arabia (S, 1877). The original limits of this red desert were the 
Sinus Saba^us to the S, the Hiddekel to the W, the Deuteronilus to 
the N, and the Phison, becoming the Euphrates, to the E. In 1879 
however, Schiaparelli restricted it to the triangle Phison-Euphrates- 
Protomlua. The drawings made by Nicsten in 1879, Wislencius in 
1890, Nicstcn and Stuyvjcrt in 1892, myself from I9 2 4 to 1928, and 
many other observers establish that Arabia is very lightly smoky Its 
red colour struck Beer and Midler, and also Sccchi; Bo-ddickcr found 
it dark orange, Cerulli reddish, Gale strongly reddish. To me, from 
Meudon, it appeared red in 191 1 and from 1924 to 1928. 

In 1879, Schiaparelli saw Arabia crossed by a bright streak, coming 
from the N. On 23 December 188 1 he wrote: 'A white, very light 



142 



band comes from the snow, across the Protonilus to the right of Coloc, 
and leading between the Phison and the Euphrates, arriving almost at 
the Lake Sirbonis.' 32 Three years later, Bceddicker followed this 
feature up to Edom Promontorium. It is the same streak as that 
passing over Edom. 

Arabia sometimes whitens near the edge of the disk, as was noted 
from Milan in 1888. This was confirmed by other observers, including 
Stanley Williams in 1892 and myself in 191 1 and 1926. 

eden (S, 1877). This is a desert country, roughly triangular, bounded 
by the Gehon to the W, the Dcutcrolnilus to the N, and the Hiddekel 
to the E. First Flammarion in 1888, then Niesten and Stuyvaert in 
1892 and Cerulli and myself in 1896-7, saw it slightly shaded. I 
confirmed this with the o m -83 in 1909, 191 1, 1924 and 1926 (Figs 
26, 27 and 43), and Quenisset also saw it from Meudon in 1924. This 
half-tone is also seen on Hubble's beautiful 1924 photograph. Eden 
appeared red to Beer and Masdler and to Secchi, dark orange to 
BcEddickcr, strongly reddish to Gale, and red to me in 1909 and 191 1, 
then rose in 1924, red in 1926 and 1928— all with the great refractor. 

Schiaparelli noted some white patches on Eden in 1 881-2, and in 
particular a whitish streak coming from the northern snows to adjoin 
Aryn; Bceddicker, in 1881, confirmed it in part. In 1886 it also seemed 
that Eden sometimes whitened near the edge of the disk, a phenomenon 
which I observed on more than one occasion. 

sphingos LACUS, Dark patch in the middle of the Hiddekel, observed 
in developed form by Schmidt in 1873. Lowell saw it in 1894, 1903 
and 1905, Moles worth in 1 900-1. I also noted it in 1903 with the 
o m -2i6 reflector (Fig 32) and I saw it well from Meudon in 1909 
(Fig 41). Sphingos Lacus is actually as large as Lake Ladoga. With 
the o m -83, its intensity appears moderate, and its colour indigo (e = 
39°). Invisible during 191 1, it was presumably pale or else veiled; 
but I saw it again in 1928. 

siloe fons (S, 1888). This is a considerable lake, situated at the 



143 



intersection of the Gehon and the Oxus, first observed by Schiaparelli 
in 1883-4 and again seen by him, as black, in 1888. Lowell drew it in 
1896-7, Douglass and myself in 1898-9, Millochau and Kibbler in 




Fig 56 Siloe Fons near the eastern edge on 19 October 
1909 (on-83 refractor) 

1901, Denning and Lowell in 1903. In 1909, with the 0^-83 refractor, 
it seemed to be extended, sombre and bluish grey (e = 16 ). g! 
Fournier observed it in 1913-14, Eriault from 1915 to 1918, Danjon 
in 1920; and Hubble photographed it in 1924. Siloe Fons is com- 
parable in area with our Great Bear Lake. 

dime pons (S, 1883-4), At about 600km from Siloe Fons there is 
another lake in the desert, of similar extent, situated at the intersection 
of the DeuteronUus and the Oxus II, which is broadened in these 
latitudes. Schiaparelli noted it in 1883-4, and saw it again in 1890, 
doubled into two short optical streaks almost parallel to the equator' 
I observed Dirce Fons in 1898^9, as did Benoit and Denning in 1903 
and G. Fournier in 1913-14. Ellison saw it as a very sombre in 
1915-16, with his o m -46 reflector. 

dioscuria (S, 1888). This land lies to the N of Arabia; it is bounded 
by the Protonilus to the S, the Arnon to the W, the Pierius to the N 
and the Pyramus to the E. It is clearly darkened; the half-tone is 
seen on sketches made by Schroeter as early as 1800. Galle, Beer and 
Midler, Secchi, Banks, Burton, Trouvelot and others have also shown 
it. With his very high magnifications, Schiaparelli overlooked the 
grcyness, as in so many other cases. From 1900 to 1903 I saw Dioscuria 

144 



easily (Figs 32, 51 and 65), and Lowell and Lampland photographed 
it in 1905. Ward even drew it as of uneven tone. 

The white streak seen from Milan in 1879 and 1881-2, between the 
northern snowy cap, Arabia and Edom, also passed over Dioscuria. 
Rather occasionally the whole region is seen to whiten under oblique 
lighting; this phenomenon was recorded by Schiaparelli in 1888, 
by Cerulli in 1898-9, and by Eddie in 1907. 

cydonia (S, 1881-2). Bounded to the S by the Dcuteronilus, to the 
W by the Mare Acidalium, to the N by the Callirrhoc and to the E 
by the Arnon, this land is decidedly smoky. The half-tone is shown 
on Schroeter's sketch made in 1800, and on those of Galle, Ma;dler, 
Secchi, Banks, Trouvelot and others. To me, Cydonia appeared 
equally dark from 1900 to 1903 (Figs 32, 51 and 65) and from 19 13 
to 19 1 6. This greyness was photographed in 1905 and 1907 by Lowell 
and Lampland. Rhcden recorded an intense red colour in this region 
in 1898-9. 

In 188 1 -2, Schiaparelli observed Cydonia to be crossed by a 
whitish streak coming from the N pole to Aryn and passing by Eden; 
it must not be confused with that coming from the same pole to Edom 
and passing by Dioscuria and Arabia. 

Cydonia is sometimes seen as white, even brilliant, when near the 
edge of the disk. This was observed by Terby in 1879, and has been 
seen by others since. Schiaparelli noted it at every opposition between 
1881 and 1890; and in 1896-7 Cerulli noted a granular appearance in 
one of these white spots. 



nix cydo.nea. Several observers have seen a bright patch, reason- 
ably brilliant, preceding the .Mare Acidalium. This patch, which does 
not seem to be due entirely to contrast, was drawn as white by various 
observers, including Lohsc in 1873, Trouvelot and Bceddickcr in 
1883-4, Denning in 1886, Meares and myself in 1896, Attkins, Moles- 
worth, Kibbler and myself in 1 900-1, Molesworth in 1903, and again 
by me in 1905. It is not always present. 



145 



IRREGULAR STREAKS AND MINOR DETAILS 

ALPHEUS (S, 1877). Recognisable as double on a drawing made in 
1830 by J. Herschel, this streak was observed as narrow and wavy 
by Schiaparelli, cutting Hellas from N to S in 1877; in 1879, the 
Italian observer saw the Alpheus at first glance. It was confirmed by 
Niesten, and also by Tacchini when passing through Milan. At this 
time it formed a cross with the Peneus (Fig 57). Schiaparelli saw it 
again in 188 1-2. Ten years later, Hussey drew here a pale streak. I 
suspected it in 1894, and in 1909, with the o m -83, I saw the northern 
half of it, knotty and extremely pale (Fig 21), 




fig 57 Alpheus and Peneus, forming a cross on Hellas, in 1879 after Schiaparelli 

(o m -2i8 refractor) 

ANUBIS (S, i88t-2). Streak on Aeria, noted on a drawing by Rosse's 
assistant in 1862. Schiaparelli showed Anubis as linear in 188 1-2. 
In 1909, from Meudon, I glimpsed it as a diffuse band (Fig 40). 

apis (S, 1888). Straight line, drawn on Aeria by Schiaparelli in 1888 
and 1890. 



arnon (S, 1883-4). Diffuse streak between Cydonia and Dioscuria, 
recognisable on the drawings made by Msedler in 1837 and by Secchi 
in 1858. From Milan, the Arnon has been seen as darker than the 
Euphrates. Lohse observed it as broad in 1883-4. At thi s time Schiapa- 
relli glimpsed it as double; in 1886, the Arnon appeared to him as 
black and broadened, but single; in 1888, double (Fig 95); and in 
1890, diffuse. Molesworth saw it on a 4*7 disk in 1899. I suspected 

146 



it as flocular, smoky and broad, and more distinct than the Euphrates, 
in 1 900-1; at that time Molesworth confirmed it, finding it distinct, 
broad and dark. In 1903 Molesworth noted it as feeble, and Millochau 
did not show it on any of his drawings. In 191 5-16, Le Coultre also 
drew it, while Ellison could distinguish it only on the N, commenting 
that it thinned off toward the S. Briault showed it as diffuse in 1918. 

aroeris (S, i 888), Straight line, glimpsed by Schiaparelli on Dio- 
scuria. 

asclepius (S, 1 88 1 -2). Lightly shaded edge of the half-tone on 
Neith Regio. Schiaparelli drew Asclepius in 188 1-2 as a very faint arm 
which broadened and became blunt toward the E (Fig 58). In 1883-4 
it appeared convex to the SSE; in 1888, broad and shaded. At the 
latter date Niesten observed it as dark, In 1903 Gale and I glimpsed it 
as the edge of Umbra. 

asopus (S, 1888). Straight line, drawn on Aeria by Schiaparelli. 

astaboras (S, 1 88 1 -2). In 1 879 this name was given to the Astusapes. 
Schrccter, in 1800, showed here a shaded border to the NE. Schiaparelli 
noted the Astaboras as a line joining Syrtis Major to Ismenius Lacus, 
which he saw single from 1881 to 1886 (Fig 58), double in 1888 and 
1890. Keeler drew the E part in 1888. In 1903 Millochau showed a 
short, wavy streak here, from Meudon (Fig 55). In 1907, Lowell and 
Lampland photographed it, as did Bernard in 1909. On these plates 
I find that the Astaboras is the boundary of a light penumbra to the 
NE, and I observed it in this guise in 1926. 

astapus (S, 1879). Irregular streak, seen by Holden in 1875 between 
the Nilosyrtis and the Nodus Alcyonius. Schiaparelli drew the Astapus 
in 1 877 ; until 1 882, it seemed to him to be convex to the S, broadened 
to the E (Fig 58); from 1883 to 1886 it still appeared to him to be 
curved; from 1888 to 1890, directed toward the NE. Hussey drew it 
in 1892. Then, in 1909 with the o m -83, I saw it as made up of two 



147 



cut-up nuclei (Fig 62), clear indigo in colour. Cerulli noted in 1896-7 
that the Astapus darkened when near the edge of the disk. 




Fig 58 View of Syrtis Major and its elongations of Nilosyrtis and Boreosyrtis, in 
iSSz-s, after Schiaparelli. This form is called the 'Scorpion' of Secclii (o m si8 

refractor) 

astusapes (S, 1 88 1 -2). A part of this wavy streak, which limits 
Meroe Insula to the W, was drawn by Msdler in 1832. In 1879 
Schiaparelli noted the Astusapes as straight, but convex to the W; 
it was sinuous in 188 1-2. From 1883 to 1890 this curvature was con- 
firmed from Milan, and seemed sometimes to be undulating (Fig 66). 
Keeler drew it diffuse in 1890. In 1 900-1 Millochau saw here a broad 
streak, which Lowell and Larnpland photographed in 1905 and 1907 
as convex to the W. With the o m -83, in 1911, I saw only the edge, 
reinforced to the S by the greyness of Meroe Insula (Fig 37), while 
at this time Graff showed it as diffuse. In 1890 the Italian observer 
found that the Astusapes was dark yellow in colour. 



148 



athyr (S, 1 88 1-2). Green drew this pale streak on Isidis Regio in 
1873. Schiaparelli observed the Athyr as thin to the N, and sinuous, 
in 1 88 1 -2 (Fig 58), but did not see it again. Holden in 1888 and Eddie 
in 1907 represented it as broad. 

borbysis. In 1909, with the o m -83, I saw a knotty, irregular streak 
separating Persea from Ausonia Borealis (Fig 20); Hale photographed 
it fifteen days later. I have again seen it, though more vaguely, at 
subsequent oppositions. 

boreosyrtis (S, 1 88 1 -2). This name was at first given to the whole 
dark, irregular curved band below Neith Regio, which joins the 
Nodus Alcyonius to the Nilosyrtis; but in 1888 the E part was named 
Casius. Since then, the name Boreosyrtis has been applied only to 
the western curvature of this great irregular streak. Secchi, the first 
to note it, drew the Boreosyrtis convex toward the N in 1856, when 
de La Rue saw it only as a shady border to the N and to the W. 
Webb represented the convexity well in 1871, and Trouvelot found 
the streak intense in 1873. In 188 1-2 Schiaparelli was struck by 
the sombre tint and the breadth of the back curve of the Boreo- 
syrtis (Fig 58). It rivalled the Nilosyrtis, then at its maximum breadth, 
and was interrupted by Boreus Pons and Asclepii Pons. At this 
time Bceddicker showed it as relatively weak. Schiaparelli again showed 
it as convex toward the NW in 1883-4, paler from 1886 to 1890 
(Fig 66). I found it feeble from 1898 to 1901, but more marked in 
1903. Lowell and Larnpland photographed it in 1905, and Briault 
showed it as a strongly shaded border of a shading to the NW from 
191 5 to 191 8. It seemed very broad to Phillips in 191 8, but less sharp 
to G. Fournier in 1920. It again appeared dark on various occasions 
to Qu6nisset in 1920 and 1922. Steavenson drew it in 1924; in this 
year it was invisible when the latitude of the centre of the disk was 
strongly negative. 

callirrhoe (S, 1 88 1-2). This great band, going from the Mare 
Acidalium to Lacus Arethusa, was drawn by Schrceter as early as 1792, 



149 



and Kunowsky represented it as very broad in 182 1-2. Beer and 
Midler, in 1837, saw it only as the shaded edge of Ortygia; but they 
and Galle drew it broad in 1839, and this was also how de La Rue 
saw it in 1856. Schiaparclli also noted it as broadened from 188 1 to 
1884; Bceddicker saw it strongly broadened in the latter year. From 
Milan, in 1886, it appeared broadened to the SW (Fig 94); it was 
double and very black in 1888 (Fig 95) and also double in 1890, 
though at this time Keeler saw it as broad and sombre. To me it 
seemed less marked from 1898 to 190 1 (Fig 51); smoky and less pale 
in 1903, when, however, Millochau did not see it. In 19 18 Briault 
noted it as the border of a shading to the N. Callirrhoe appeared 
sinuous to Schiaparclli before its doubling in 1890. 

casius (S, 1888). This is the E part of the original Boreosyrtis; it 
consists of the dark, broken and knotty SW edge of the shading of 
Utopia. It was recognisably dark on Schrceter's sketch of 1785, and 
this extraordinary streak appeared diffuse on drawings made by Galle 
in 1839, Masdler in 1841, Secchi and de La Rue in 1856, and Secchi in 
1858. Almost all observers agreed in showing the Casius as the border 
of the sombre surface of Utopia. Yet from 1 881 to 1890 Schiaparelli 
drew it only as a streak, moderately broad and dark (Fig 58), which 
sometimes doubled in 1888 and 1890. The clear visibility of the geo- 
metrical canals is undoubtedly accompanied by the disappearance of 
the real half-tones. 

The intensity of Casius varies together with that of Utopia; it 
seemed to be at its greatest in 1785, 1841, 1883-4, '888, 1898-9 and 
1903. Millochau sometimes drew it decidedly dark from 1900 to 1903 
(Fig 147). In the latter year I noted that the band had a knotty struc- 
ture (Fig 59), confirmed by Molesworth, the Fournier brothers, 
Briault and Thomson. Briault drew the Casius blackish in 1915-16 
and in 1917-18, and to me appeared very dark in 1926 and 1928-9. 
Thomson saw the Casius brown to the N in 1918 (e = 178 ); to me, 
it was greenish in 1928^9 (e = 86° and I03 °). It seems, therefore, that 
the band changes partially from green to brown in the northern summer. 
According to Cerulli, the visibility of Casius increases near its edge; 
I have confirmed this. 



150 




Fig 59 Casius seen breaking into the edge of the shading of Utopia, n April T903 

(p"'.2i6 telescope) 



deuteronilus (S, 1 88 1 -2). This is a part of the old Nilus, but is less 
distinct than the Protonilus, Kunowsky, the first to see it, represented 
the Deuteronilus in 1 821-2, when it was broad and intense. Beer and 
Msedler also noted it as broad from 1837 to 1841, as did Galle in 1839. 
Dawes drew it narrow in 1864. Trouvelot observed it in 1873, Schiapa- 
relli from 1877 t0 I ^9». Bceddicker in 188 1-2, and Keeler in 1890. 
Millochau represented it as diffuse in 1900-1, but did not see it in 
1903, and I have always found this object very feeble (Fig 51). In 
1888 Terby saw the Deuteronilus as rosy. 

Euphrates (S, 1 879). Broad streak, irregular and continuous, coming 
from Portus Sigeus to the Lacus Ismenius, and limiting the shading of 
Arabia. Msedler, the first to see it, showed a greyness to the N of the 
Sinus Sabseus in 1837, confirmed by Kafser in 1864. Schiaparelli 
represented the Euphrates as wavy and narrow in 1877, and called it 
the Phison; he saw it as irregular in 1879, when Niesten could make 
it out only as the edge of the shading. To Schiaparelli it was double 
from 1882 to 1884, single in 1886 and double in 1888 and 1890. 
According to him, in 1888, the Euphrates, together with the Arnon 
and the Kison, pivoted by io° to the right around the Portus Sigeus, 
but to me this seems incredible, Bceddicker noted the Euphrates as 
diffuse from 1881 to 1884, Niesten irregular in 1888, Keeler broad 
and knotty at the same time. Hussey and Schiaparelli saw it broad 
to the S in 1892. With the o m -83 Idrac saw it excellently in 1909 as 
a greyish band, broad and diffuse, of irregular intensity and breadth, 

151 



and apparently continuous. I saw it, to the S only, from Meudon from 
1909 to 1928 as broadened, smoky and diffuse (Fig 41), and I was able 
to follow it in 1927 on an 8*- 2 disk. Cerulli found the Euphrates easier 
to see when near the edge of the disk, and from Milan in 1890 it 
appeared reddish. 

euripus 1 (S, 1877). On his 1877 map, Schiaparelli gave the name 
Euripus to the greyish band separating Hellas from Chersonesus; in 
1879 he saw it extending up to the Mare Tyrrhenum. For convenience 
in description, I have divided this streak into two parts. The upper 
section was seen by Beer and Majdler in 1830, when it showed up 
the fact that Hellas is an island. The strait was drawn by Secchi in 
1858, and has been seen by all observers since then. In 1877 the Henry 
brothers drew it as broad, but at this time Schiaparelli commented on 
its narrowness as far as latitude 52 ; however, he made it broader 
from 1879 to 1882. With the o m -83 in 1909 I noted it as very pale 
(Fig 19), and this was confirmed on the photographs by Barnard and 
Hale. To me it seemed more in evidence in 1924, 1926 and 1928. In 
1924 the colour of Euripus I was brown (e = 358 and 337 ). 

euripus 11 (S, 1879). This is the part of Euripus which divides the 
two Ausoniae. Recognisable on the 1830 sketches of Beer and Msedler, 
this boundary was noted by various observers as being of uneven 
tone— for instance by Kaiser in 1862 and 1864. In 1879 and 188 1-2 
Schiaparelli saw it as a broad diffuse streak, confirmed by Schseberle 
in 1892. Hale and Barnard photographed it in 1909 as the intensified 
boundary of the shading of Ausonia Borealis. My drawings from 
Meudon agree with this (Fig 33). 

euryalus (S, 1890). Line glimpsed by Schiaparelli to the S of the 
Callirrhoe. 

gehon 1 (S, 1877). Broad variable streak, irregular and complex, 
and making the boundary of the shading of Eden. It is curvilinear, 
and curves, convex to the W, from the Sinus Meridian! to Siloe Fons. 
J. D. Cassini was the first to represent it, in 1666 (Fig 42). In 1877 

152 









Schiaparelli drew the Gehon I as very concave toward the right, and 
he found it easy in 1879, when Burton also observed it. In 188 1-2, 
from Milan, it appeared to fade away toward the left. Niesten saw it 
only as the edge of the penumbra of Eden ; but Boeddieker showed it 
broad and diffuse, and it was the same to him in 1883-4. From 1883 
to 1886 Schiaparelli always thought the Gehon concave to the W; in 
1 888 and 1 890, rectilinear. Holden showed it as very marked in 1 888 
and 1890, In 1892, Schiaparelli again saw it curved. I first observed 
it from 1894 to 1898-9. Stanley Williams and Cerulli saw it as double 
in the latter year. Subsequently I saw it as broad, intense and very 
easy in 1900-1, together with Flammarion and Touchet; in 1903 
Mtllochau saw it as feeble, knotty, and concave to the E. Using the 
i ra "52 Mount Wilson reflector in 1909, Hale resolved the Gehon into 
minute filaments, twisted and curved back; as a whole the streak was 
neither straight nor rectilinear. This marvellous result, which sur- 
passed anything previously attained for Mars, is as much to the credit 
of the eminent American astronomer as to that of the great reflector 
he was using. With the o m *83 I observed the Gehon as the border of 
Eden, very lightly shaded, in both 1909 and in 191 1, when it appeared 
broad and intense (Fig 60). Briault showed it as very broad in 191 5- 
16, as did Quenisset in 1922. From 1924 to 1928 it appeared to me to 
be extremely pale, bordering the almost imperceptible half-tone to the 
left (Fig 43), but it had become broad, intense and chestnut-coloured 
in March 1929 (e = 135°). 

hadria. Broad, variable streak between Hadricaum Mare and Pro- 
methei Sinus, separating Chersonesus from Ausonia. It was observed 
by Schiaparelli in 1892, and by Schaeberle, Campbell and Keeler in 
1894. 

heliconius (S, 1 88 1 -2). Lower, sometimes reinforced edge of the 
dark shading of Utopia. Beer and Maedler noted it in 1839 and 1841, 
when it was very marked. De La Rue observed it in 1856 in the form 
of a streak. Secchi in 1858, Burton in 1871, and Trouvelot, Flammarion 
and Green in 1873 showed it as the border of the greyness to the S. 
BcEddicker confirmed this in 188 1-2, when Schiaparelli drew Heli- 



153 



conius as very black, without seeing the adjacent shading. Despite 
the linear aspect seen from Milan from 1883 to 1886, and the doubling 
in 1888 and 1890, Millochau, in 1903, drew the Heliconius as very 
broad and sombre (Fig 147), and I have always observed it as the 
diffuse edge of the greyness of Utopia (Fig 59). 




Fig 60 Gehon seen on 29 September 1911 {0*1-8} refractor) 

hiddekel (S, 1 877). An irregular, complex and variable streak, 
concave to the SE, going from the Sinus Meridiani to the Lacus 
Ismenius, and bordering the penumbra of Eden. Maedler, in 1841, 
saw it only as the boundary of the greyness to the W. Trouvelot 
observed it as dark at the edge of the disk in 1873; H olden saw it pale 
in 1875. SchiaparelU saw the Hiddekel irregularity wavy in 1878, on 
a 5*7 disk! Burton and Dreyer glimpsed it in 1879, when it was missed 
from Milan. Niesten, in 1881-2, saw it as the boundary of the shading 
to the W; SchiaparelU saw it from the end of 188 1 to 1896, slightly 
convex to the NW, but never double. Keeler drew it diffuse in 1890, 
as did Campbell in 1894 and Millochau in 1900-1. With my o m -2i6 
reflector in 1903 I saw the NE extremity as a blackish horn coming 
from Ismenius Lacus (Fig 65). In 1909 Hale resolved the Hiddekel, 
like the Gehon, into minute filaments, twisted and curved back, and 
which in this great telescope were neither straight nor rectilinear. This 
shows the enormous power of the i m *52 mirror. Using the ow-83 at 
this time, I saw the Hiddekel as the boundary of the feeble half-tone 
of Eden; in 191 1 I saw it broad and curved; in 1924, as the slightly 
greyish boundary of Eden (Fig 43). The same aspect was seen in 
1926. 




HOR. Diffuse band, observed by Millochau from 1900 to 1903, 
joining the Nilosyrtis to the Triton. 

hyllus (C, 1897). Broken streak, cutting Noachis from the NNW 
to the SSE. Kaiser drew it in 1864, and it was again seen by Cerulli 
from 1896 to 1899. I confirmed it at Meudon in 1909 (Fig 24), when 
Barnard photographed it. It was again broad, irregular and brownish 
in 1924 and 1926. 



IXION (S, 1890). 
Ismenius Lacus. 



Line glimpsed by SchiaparelU in the NNW of 



LABOTAS (L, 1894). Irregular band, emerging from Portus Sigeus 
and going toward the NW. Schaeberle drew it as knotty in 1892. In 
1 909, from Meudon, I saw it convex to the NE, pointed at the extremi- 
ties, and intense (Fig 41); but no trace of it remained in 191 1, nor in 
1924. 

nasamon. Temporary streak, bounding the shading of Neith Regio 
to the SE. This is the form in which the Nasamon is shown on the 
sketches made by Hooke in 1666, and Herschel in 1777 and 1779. 
Schrreter described a band here in 1785. Neither Beer and Maedler 
nor Secchi saw it. It was represented as a shady border by von 
Franzenau in 1864, by Burton in 1871, by Trouvelot in 1873 and by 
Terby in 1875. Burton and Niesten saw it sombre in 188 1-2, and 




C '.' ■* 



Fig 61 View of part of Syrtis Major tvith Nasamon, 7 December 1896 {0^-240 

refractor) 



154 



155 



Bceddicker distinguished it only as the boundary of the half-tone of 
Neith Regio in 1883-4. I found it easy from Juvisy in 1896-7 (Fig 6r) 
and this was confirmed at the same period by Schiaparelli. Moreux 
also saw it at this time. It was visible, though feeble, in 1926 with the 
o m *83. 

nepenthes (S, 1 877). Irregular, changeable streak, broad and convex 
to the S, where it is bounded by the greyness of Libya and Lacus 
Mceris. The W part was drawn by Dawes in 1864. Webb showed it as 
more extended in 187 1. In 1877 Green saw it only as the border of the 
shading to the S, but Schiaparelli showed it as a very sombre parabola 
(Fig 46), shortened to the W in 1879 ( Fi g 47)- In 1881-2 the Nepenthes 
seemed to him to be broad and very black (Fig 48); Niesten could 
distinguish it only as the border of the shading to the S, a little less 
marked from 1883 to 1886, when it formed the boundary of the shad- 
ing of Libya. Schiaparelli again found it very intense, then double, 
from 1888 to 1890; it always limited the half-tone to the S. In 1888 
Holden drew it as blackish and enlarged. In 1894, Campbell drew it 
only to the W, and in 1903 Millochau represented it as knotty and 
feeble. From Meudon, in 1909, it appeared to me simply as the border 
of Libya and Lacus Mceris (Fig 62), convex to the S. In 191 1, G. 



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156 












Fournier noted it as dark, and from 6 September, with the o ra -83, I 
saw it as very enlarged, broken up, knotty and very sombre; it was 
like this on 9, 13 and 14 November (Figs 37 and 63), but was rather 
less marked in December. Graff then saw it as the boundary of the 
shading of Libya. From 191 3 to 1916 it seemed to me to have the 
same aspect. Quenisset, Briault and Thomson noted it as equally 
evident in 191 8, as did Phillips, Gale and Thomson in 1920 and 
Danjon in 1922. In 1924 I noted that while it remained broad and 
irregular, it appeared clearly pale; but it was darker than ever in 
1926-7 and 1928, and was visible even on a 7*'7 disk. Danjon photo- 
graphed it excellently in 1926. Thus the Nepenthes was blackish in 
1888 and also from 191 1 to 1928 inclusive; we have here strange 
changes in an irregular period. 

neudrus (L, 1894). Reasonably intense E border of a grey area 
covering the extreme right part of Deucalionis Regio. It is the same 
feature as that drawn in 1879 by Burton. Schiaparelli, in 1890, drew 
a diffuse shading here. Two years later, Barnard saw it as a double 
streak. With the o m *83 in 1909 I noted a vague shading (Fig 26), and 
Hale photographed it several days later. The aspect was the same in 
191 1. Then, in 1924, I drew it as the E border of the half-tone (Fig 
43), and this was confirmed by the photographs obtained by Hubble 
with the great Mount Wilson mirror, I again confirmed it in 1 926 and 
1928. 

nicenus (S, 1890). Straight line glimpsed by Schiaparelli on Isidis 
Regio. 

nilosyrtis (S, 1 88 1-2). This is the NE part of the original Nilus 
and the greatest artery on the planet. It links Syrtis Major to the 
Coloe Palus, and appears as a curvilinear line, convex to the E, very 
broad and very irregular. Secchi saw here the 'Scorpion's Tail' of the 
Syrtis. The axial inclination of Mars means that at perihelic opposi- 
tions it is often veiled by yellow clouds when near the edge of the 
disk. The Nilosyrtis is recognisable, in the S part, on Herschel's 



157 






sketches made from 1777 to 178 1, Schrceter's between 1785 and 1800, 
and Kunowsky's in 1S21-2. J. Herschel drew it very broad and 
blackish in 183 1, and it is strange that Maedler did not note it before 
1 841. Its general form was first represented by Galle in 1839. De La 
Rue in 1856, Secchi in 1858, and von Franzenau in 1864 drew it as 
broad and very dark. In 1864 Dawes gave it a curvature which was not 
confirmed by later observations. It was intense and extremely broad- 
enlarged to 12 — to Burton in 187 1, and Trouvelot made it a full 8° 
in 1873 (Fig 50). Still broad and dark to Green in 1877, it appeared 
blackish to Schiaparelli, and was the same in 1879. Schiaparelli found 
the Nilosyrtis quite black in 1882,* and extremely broad -8°, almost 
equal to the Maria Tyrrhenum and Hadriacum (Fig 58). As seen from 
Milan, the aspect in 1883-4 was much the same, but it was feebler in 
1886. Perrotin, Holden and Keeler saw it very broad and dark in 
1888; Schiaparelli, straighter than from 1882 to 1884, but more en- 
larged and irregular in 1890 (Fig 66). Subsequently, Young and Hussey 
observed the Nilosyrtis as broad, intense and irregular in 1892. From 
1894 to 1 901 it did not seem to me to be striking, but from 1900 to 
1903 Millochau showed it large and dark with the o ra -83 (Fig 64). In 
1905 the photograph by Lowell and Lampland showed it excellently; 
it was then dark. With the great refractor, it was seen to be veiled 
by citron-yellow clouds in 1909, except sometimes to the S, where its 
root seemed to me to be very well-developed and filamentary (Fig 
39). This was partly confirmed by the photographs taken by Barnard 
and by Hale. In 191 1 I saw it as very beautiful— large, irregular and 
dark (Fig 37) ; it was then as broad as the Red Sea, but in 1924 I noted 
that it was always very feeble or veiled by yellow clouds, except on 
one occasion to the S. Still pale in 1926, it appeared easy in 1927 on 
a disk subtending only 8"o. Finally, in December 1928 it was very pale. 
^ In 191 1 I was surprised to see the Nilosyrtis emerging from the 
Syrtis Major and proceeding not to the N, but to the NE, to be 
subsequently deflected to the NW almost at a right angle. This 

•The fact that Schiaparelli so often noted black spots on Mars is due to his using 
a red or yellow filter in front of his eyepiece, thereby weakening the light of the dark 
bluish areas of the planet. 



structure can be vaguely suspected on the early drawings made by 
Herschel and Schrceter; it is better shown on those of Boeddicker, and 
it is excellently shown on those by Millochau (Fig 64). The photo- 




Fig 64 Nilosyrtis, 22 February 1901, after Millochau {o m -S3 refractor) 

graphs taken by Lowell and Lampland in 1905 and 1907 confirm this 
aspect. This great streak has often been observed as the most intensely 
shaded part of the border of Neith Regio, as seen on the drawings of 
Herschel and others. To Schiaparelli in 1879 it seemed to be constric- 
ted toward Coloe Palus. Nilosyrtis seemed blue to Secchi, and a sombre 
bluish grey to me from Meudon in 191 1. 

Orion (S, 1890). Line glimpsed by Schiaparelli between Ismenius 
Lacus and Pierius. 

orontes (S, 1879). Irregular light grey feature, curved and concave 
to the SSE, joining the Euphrates to the preceding horn of the Sinus 
Meridiani. In 1877 the Henry brothers drew here a light shading to 
the N. In 1879 Schiaparelli showed a line, noticeably curved inward, 
Subsequendy he described the Orontes as very much in evidence, 
and double from 1882 to 1886; m 1888 it appeared to him as rectilinear; 
in 1890, again double; in 1892, straight. Hussey at this time saw it as 
diffuse. With the o m -83, I generally see it as an excessively pale half- 
tone in the N part of Edom (Fig 43). 



158 



159 




CM A 






Fig 63 Oxus, knotted, with Dirce Pons, Sttoe Fons, Coloe Palus and hmenius 
Lacus darker, 6 April 1903 {o m -2i6 telescope) 

oxus 11. This is the Eastern Oxus of Schiaparelli in 188 1-2, and 
the 'Djihoun' of Lowell, who joined the Margaritifer Sinus to the 
Ismenius Lacus by a curved feature, convex to the NW, knotty, in- 
tense and variable. Galle drew it as very broad and dark, and as the 
border of the Oxia shading, in 1839. Majdler in 184 1 and Secchi in 
1858 also showed it. In 1873 Trouvelot observed it as very much 
enlarged, and Intense; Green showed it as more diffuse. Boeddicker 
and Schiaparelli saw it in 1 881-2; Schiaparelli found it very evident 
in 1883-4 and 1886, but never saw it again. Cerulli observed it in 
1898-9, In 1903 I classed it as easy; with the o m -2i6 reflector it then 
appeared narrow to the SW, but greatly broadened in a knotty curve 
toward the W (Fig 65). At this time Millochau drew it as intense. 
In 1905 I confirmed this structure. To Briault, it was very strong in 
191 8. I again noted it as enlarged to the left in 1924, and this aspect 
was once more seen, on a f"-o disk, in March 1929. 

parnes (S, 1890). By this name Schiaparelli indicated a line which 
he glimpsed parallel to the Thoth, and going from the Nodus Alcyonius 
to Cyllenius Lacus. I have given the name Parnes to the S prolonga- 
tion of the Thoth I, up to Syrtis Minor. The 1888 colour chart by 
Schiaparelli gives the name Amenthes to a line joining Nodus Alcyoniua 
to Syrtis Minor; this is inaccurate, as Amenthes is the continental 
region to the E. The variable streak Parnes was first shown in recog- 
nisable form on a drawing made by Holden in 1875. Schiaparelli 

160 



observed it from 1881 to 1884 and in 1890. In 1894 Stanley Williams 
drew it as very broad, double and blackish ; with Moreux, I saw it in 
1896; Millochau noted it in 1903; and in 1924 I saw here a broad, 
irregular streak, going on to join the Thoth I. 

peneus (S, 1879). Ill-formed, very feeble streak which Schiaparelli 
saw crossing Hellas in an E-W direction (Fig 57). In 1862, Knott 
drew three short tracks here; in 1864, Kaiser showed a shading going 
from the Mare Hadriacum to the centre of Hellas. From 1879 to 
1882 Schiaparelli saw here an easy grey streak, forming a cross with 
the Alpheus. In 1894 I glimpsed the Peneus; in the area Campbell 
drew a vague shading at this time. In 1909, with the o m, 83, I noted a 
very feeble streak. 

PHISON (S, 1877). This name was first given to the Euphrates, and 
then, in 1879, to the broad, irregular streak joining the Portus Sigeus 
to the Nilosyrtis and bounding the half-tone of Arabia. Following 
Schiaparelli, Kaiser saw the Phison in 1864. Trouvelot, in 1873, saw 
only the middle part (Fig 50), but in 1877 the Henry brothers saw it 
as the border of the shading of Arabia, an aspect confirmed by Niesten 
two years later. In 1879 Schiaparelli distinguished only a fine line, 
dark and slightly curved; in 1882 he saw two lines which looked as if 
they had been drawn with a ruler (Fig 58). At this time Niesten saw 
the streak as narrow and sinuous ; to Bojddicker it was broad and pale, 
and like the smoky border of Arabia. Schiaparelli again drew the 
Phison double in 1883-4; Boeddicker saw it simply as the grey border 
mentioned above. In 1886 it was noted as single from Milan, while 
Perrotin saw it doublet Schiaparelli and Perrotin again observed it as 
double in 1888. In 1890 the Italian astronomer saw it first as broad 
and irregular, later as double; Keeler noted it as diffuse to the SW. 
Schiaparelli again drew it narrow in 1892 and broad in 1894, but 
Millochau drew it undulating and knotty in 1903, except at its S end. 
In 1909 Idrac made an important observation with the o m *83, and 
glimpsed the Phison as a continuous band of shading, broad and 
diffuse, and of irregular intensity. From Meudon, in 191 1, it appeared 



161 



to nve as broad, sinuous, irregular and very feeble (Fig 37), and 
forming the edge of the half-tone to the NW. Then m 1924, 1926 
and 1928 I again glimpsed it as broad and very pale. It is worth noting 
that Schiaparelli described the Phison as brownish-red in 1881-2 and 
reddish in 1888 and 1890. 

pierius (S, 1883-4). Broad irregular streak, formerly very dark and 
visible in small instruments, joining the Boreosyrtis to the Arethusa 
Lacus, and bordering the shading of Cecropia. The Pierius was first 
drawn by Kunowsky in 182 1-2, and it was also beautifully shown on 
the 1839 drawings of Maedler and Galle. It was still striking in 1841, 
according to Maedler. Brodie again observed it as broad and intense 
in 1856, as did Secchi and Dawes in 1858. Although Flammarion 
and Trouvelot saw the Pierius broad and dark in 1873, Green dis- 
tinguished it only as the edge of the half-tone to the N. Schiaparelli 
saw it with difficulty in 188 1-2. Like Boeddicker, he found it feeble 
in 1883-4; Trouvelot then distinguished it only as the border of the 
grey area. It was still pale as seen from Milan in 1886. Holden, Keeler 
and Niesten represented it as broad, irregular and dark in 1888, but 
Terby noted it as rather feeble, and Flammarion described it as the 
border of the smoky Cecropia. At this time Schiaparelli said that it 
was double and very black. In 1890 Keeler again saw it broad and 
prominent; to Schiaparelli it was less marked, and irregular (Fig 66). 
To me it appeared diffuse and pale; to CeruIIi in 1898-9, more in- 
tense, and in 1 900-1 he saw it as the border of the smoky area of 
Cecropia (Fig 51). This was confirmed, in part, by the observations 
made by Millochau in 1901. Galle, Millochau and I noted it as quite 
broad in 1903 (Figs 32 and 55). Two years later Lowell and Lampland 
photographed it as the boundary of the shading of Cecropia. This was 
confirmed by Briault in 1918. 

POROS. Line glimpsed in 188 1-2 by Schiaparelli, separating Pharos 
Insula from the continent of Aeria (Fig 58). In 1890 it was noted as 
double from Milan. 







Fig 66 Protonilus, contracting to the East, 16 May i8go, after Schiaparelli 

{o m -4Q refractor) 

protonilus (S, 1 88 1 -2). This is the second segment of the old 
Nilus, joining the Nilosyrtis to Ismenius Lacus. It makes up a great 
artery which is irregular, easily seen, knotty and sombre, curved back 
to the E, and to the N bordering the half-tone of Dioscuria. The 
Protonilus was first represented by Kunowsky in 182 1-2. 38 In 1839 
Beer and Msedler, and also Galle, drew it recognisably, and moreover 
Galle saw the edge of the grey area to the N. In 1841 Msedler observed 
it as still more prominent. It appeared broadened to de La Rue and 
to Brodie in 1856, and to Secchi in 1858. Kaiser, in 1864, noted it as 
narrow, while Dawes gave it a bend convex to the N. In 1873, Flam- 
marion and Terby saw it on a small disk, using an o m -io8 refractor. 
Trouvelot at that time drew it very broad and sombre (Fig 50). It 
seemed narrow to Schiaparelli in 1877 and 1879, and also to Holden 
in 1879. Boeddicker found it diffuse in 188 1-2, Schiaparelli broad. In 
1883-4 Trouvelot represented it as strong, Schiaparelli as pale, and 
Boeddicker as the boundary of the shading to the N. In 1886, from 
Milan, it still appeared weak. In 1888 Perrotin, Niesten, Keeler and 
Holden saw it broad and dark. Holden also noted the shading of 
Dioscuria; Schiaparelli described the band as double and very black, 
as he also did in 1890. In 1892 Young saw it as broad and prominent. 
From 1896 to 1901 I found it feeble, sometimes only as the boundary 
of the greyness below (Fig 51). In 1 900-1, with the o m -83, Millochau 
observed it as diffuse. In 1903, when I found the feature showing up 
as the border of the shading (Fig 32), Millochau drew the Protonilus 
broad and patchy. Lowell and Lampland photographed it in 1905, as 



162 



163 



separating the bright country to the S from that to the N. In 1909 I 
saw it excellently from Meudon, strongly curved by perspective at 
6i° from the centre of the planet's disk; and in 191 1 it appeared to 
me as wavy and dark. In 1924 it was veiled by yellow clouds, and re- 
mained invisible during the whole of the opposition. 

The Protonilus narrows to the E, near Coloe Palus; Trouvelot first 
drew it thus, in 1873 (Fig 50). In the same year Terby, using an 
o m *io8, showed it interrupted — a very remarkable observation. In 
1875 Holden represented it as narrow to the E, and in 1888 Schiaparelli, 
Perrotin and Keeler saw a discontinuity or a narrowing in this position. 
Then, in 1890, the E part of the Protonilus appeared filamentary from 
Milan (Fig 66), and this was confirmed in the same period by Keeler. 
Millochau again saw this aspect in 1903. Some indentations in the 
Protonilus were noted by Niesten in 1888 and by Schiaparelli in 1890 
(Fig 66), and Cerulli saw here a knotty structure in 1 898-9. 

pyramus (S, 1883-4). Band glimpsed by Schiaparelli from 1883 to 
1890, between Coloe Palus and the Cydnus. Molesworth noted it as 
broad and dark in 1903. 



sitacus (L, 1894). The configuration of darkish spots between 
Coloe Palus and Sinus Meridiani, which can sometimes be glimpsed 
in the guise of a line, was named Sitacus by Lowell. In 188 1-2 
Bceddicker drew a broad, ill-defined streak in this direction, near 
Coloe Palus; Cerulli from 1896 to 1899, and Denning in 1903, showed 
an illusory straight line here. 

thoth 1 (S, 1877). Broad, knotty streak, broken-up and very 
variable, and convex to the ESE, going from the Nepenthes to the 
Nodus Alcyonius. It was first described by Galle in 1 837, who called 
it very broad and diffuse. Webb in 1871, Green from 1873 to 1877, 
also saw it. Schiaparelli observed the Thoth in 1878 on a 6* disk; in 
1879 it seemed to him to be broadened to the N, and in 188 1-2 he 
showed it as doubled (Fig 58). At this time Niesten described it as 
broad and diffuse. The Italian observer saw it again in 1883-4, w ^ tn 



164 



Boeddicker, and yet again in 1886. A great development took place 
here in 1888. Niesten, Perrotin, Terby and Keeler drew the Thoth 
as very broad and very sombre, while Holden called it blackish; at 
this time Schiaparelli noted it as intense and double, and he saw it 
similarly in 1890, when his 'Parnes' was regarded as the eastern 
branch of the gemination. Neither Keeler nor Schasberle drew it in 
1892, but Stanley Williams noted it as double and very intense in 
1894. Cerulli, who distinguished it on a 7* disk, described here in 
1896-7 'an extremely complicated and indecipherable system of dis- 
tinct and extremely thin patches'. 84 In 1903 Millochau observed it as 
knotty, and I confirmed this in 1909 with the o m, 83 (Fig 62). Then, 
in 191 1, there came an even more striking intensification. First G. 
Fournier, and then I at Meudon, saw it extremely developed, very 
much broadened, and strikingly broken-up (Fig 63). This aspect per- 
sisted from 1 913 to 191 6, because I could always see the band as 
broad and intense. Quenissct, Briault and Thomson still found it 
striking in 1918, and Danjon in 1922 described it as broadened and 
very beautiful. With the o m -83 I again saw it broad in 1924, but its 
intensity seemed to be less. The Thoth was extremely sombre, very 
broad and knotty in 1926-7, when Danjon photographed it, and also 
in 1928. With Nechville, in 1927, 1 was able to follow it on a *}*-"j disk 
of Mars, using a magnification of 1250 on the o m *83. 

The developments of the Thoth in 1888 and in 191 1 went together 
with those of the Nepenthes, and are not of a seasonal nature, because 
it kept its great intensity for eighteen years following the remarkable 
observation made by G. Fournier on 6 September 191 1. Cerulli has 
found that the Thoth is most prominent when seen under oblique 
lighting. To me, in 191 1, it appeared bluish grey. 

thoth 11. The N prolongation of the Thoth I. In 1888 Schiaparelli 
and Smart drew a line here, again seen by Rheden in 1898-9. To avoid 
confusion, I have divided the old Thoth into two parts. 

TRITON (S, 1877). Darkened border of the shadings of Hesperia and 
Libya, joining the NW point of the Mare Cimmerium to the Tritonis 



165 



Lacus. SchiaparelH found the Triton very easy in 1877, but observed 
it only from the Syrtis Minor to the Tritonis Lacus (Fig 46). From 
1879 to 1896 he saw it throughout its length; he noted it as 'one of the 
most beautiful of the canals', in 1879, with three small undulations on 
its two banks (Fig 47), but from 188 1 to 1886 it seemed to him to be 
less striking. In 1888, as seen from Milan, the Triton was transformed 
into a gulf of the Mare Cimraerium, making up the boundary of the 
shadings to the SW, and in 1890 it was seen as double. Millochau 
observed it from 1900 to 1903. In 1909, with the o m -83 and with 
superb images, I could distinguish it only as the border of the shadings 
to the SW, and enhanced by the alignment of the Cyllenius Lacus and 
the Libycae Paludes (Fig 62). This was also how Graff noted it in 191 1, 
though in less detail. 

typhon (S, 1879). Known also as Typhonius on Schiaparelli's pro- 
visional map of 1886, this indefinite streak makes up the border of a 
very light grey area to the NE. It was observed thus by the Henry 
brothers in 1877. Schiaparelli found the Typhon linear, but difficult, 
in 1879; to him it seemed double from 1882 to 1824, single in 1886, 
double in 1888, single again in 1890. Schzeberle sketched it as broad 
in 1892, as did Maunder in 1894. In 1909, with the o m '2i6 reflector, I 
glimpsed it as a more or less straight band ; but in the o m -83 it seemed 
only to be the border of an extremely feeble half-tone to the N (Fig 
26), and it was in this form that I again saw it from Meudon in 1924 
and 1926. 

XENIUS (S, 1883-4). Line sometimes glimpsed as a pen-stroke by 
Schiaparelli from 1883 to 1890, between Dirce Fons and Arethusa 
Lacus (Fig 95). In 1905 Ward drew a shading here, as did Danjon in 

T920. 

References 

1 Flammarion, La Planfctc Mars, VOL 1, p 436. 

2 Mart net 1896-7, p 54. 

3 This was noted by Schiaparelli (Memoria, I, 91). 

4 Two months after the publication of my results, Comas Sola published a note 



166 



claiming that he had confirmed in part, this curious leopard-skin appearance 
(Bull Astr Soc France, vol 24 {1910), 37). 

5 Terby, Ariographie, 38. 

6 Memoria, II, 85. 

7 Memoria, III, 65. 

8 Memoria, VII, 48. 

9 Bull Astr Soe France, vo 13, 1899, 264. 

10 Memorie deU'Osseevatorio del Coltegio romano, vol 1 , 2 1 . 

11 Terby, Ariographie, 55. 
11 Op dt, 21. 

13 Terby first noted this fact {Ariographie, 8, 9, 59). 

14 Ariographie, 74 and 75. 

15 Flammarion, La planite Mars, vol 1, 125. 

16 Terby, Ariographie, 94. 

17 Memoria, III, 65. 

18 Memoria, IV, 47. 

19 See Figs 11 and 13. 

20 It was Flammarion who first suggested changes here (Laplanete Mars, vol I, 148). 
31 Bull Astr Soc France, vol 23, 489. 

22 Memoria, II, 69, and Trans Roy Dublin Soc, vol 1, 2nd series, 302-3. 

23 Memoria, I, 85. 

24 Memoria, II, 86. 

25 Flammarion, op cit, vo] 1, 441. 

26 Memoria, III, 69. 

27 Memorie detla Socicta degli spettroscopisti italiani, vol 11, 26. 

28 Flammarion, op cit, vol 1, 441. 

29 Trans Roy Dublin Soc, vol 1, 2nd series, 302. 

30 Terby was the first to recognise this identity of Utopia on Huygens' drawings 
{Ariographie, 9). 

31 Memorie delta Societa degli spettroscopisti italiani, vol it, 1882, plate. 

32 Memoria, III, 82. 

33 Terby was the first to notice this (Ariographie, 47). 

34 Martenet, 1896-7, 105. 



167 



Margaritifer Sinus, Aurorae Sinus, 
Solis Lacus and Marc Boreum 



MARE Oceanidum. This is the sea to the S of Noachis and 
Argyrc I, first clearly recognisable on a drawing made by Lassell 
in 1862, and which I saw as brown in 1924 after 18 August 
(e = 327°), 

CHALCE. Vague island, bordering upon Noachis, and observed 
by Schiaparelli from 1879 to 1882 to the E of Argyre I. It then 
appeared smokier than Argyre 1, and this was how I saw it from 
Meudon in 1924 (Fig 67), when its colour was a sombre red brick. 

A white projection on the terminator was seen in this area by 
Molesworth on 7 February 1897. 

In 1881-2, from Milan, another island was seen to the N of 
Argyre I, less luminous than Noachis. 

ARGYROFOROS. Straight separating Chalce from Argyre I. It was 
recognisable on drawings made by Secchi in 1858, Kaiser in 1862, 
Dawes in 1865, Trouvelot in 1877 and Schiaparelli in 1877 and 
1879. This channel has been frequently observed since, and has 
sometimes appeared dark to me with the m '83 refractor (Fig 67). 

argyre I (S, 1877). This celebrated island of the Mare Eryth- 
raeum, with an area comparable with that of our New Guinea, lies 
on the 48th south parallel, 1200km from the coast of Thaumasia. It 
is vaguely shown on the sketches made by Beer and Maedler as early 
as 1830, joined on to Noachis and the island to the left. It is the 
third land in the great chain of islands which goes from Noachis to 




Ogygis Regio. Its insular character is shown on Secchi's drawings 
of 1858. In 1877 Schiaparelli showed its form excellently as an 
irregular pentagon, somewhat elongated E-W, with a point to the 
N. I confirmed this aspect in 1924 and 1926, from Meudon (Fig 
67). 




Fig 6y Argyre I hi 1924. (o m -Sj refractor) 

Argyre is much less bright than the continents. This is shown on 
Herschel's sketches made in 1783, and on those of a great many 
other observers, as well as on photographs. In 1879 Schiaparelli 
found that in Argyre the shading lightened gradually from E to W, 
where the island was best defined. The colour of this desert land 
appeared red to Secchi, reddish to Trouvelot, very red to Flam- 
marion, uneven red to Schiaparelli and a vivid brick red, some- 
times smoky, to me with the great refractor. 

Yellow clouds may give an orange or golden tint to Argyre, 
depending on their thickness. Sometimes they obliterate it com- 
pletely, as I and others found in 1911. But the most remarkable 
phenomenon of Argyre I is undoubtedly the ease with which it 
whitens, more markedly than any other land, under oblique light- 
ing, sometimes when the planet is a long way from perihelion. 
Schiaparelli wrote: 'Under certain circumstances, this island be- 
comes so brilliant near the edge of the disk that observers have 
been deceived into believing it to be a polar cap. This intense 
brilliancy was noted by Dawes in 1852; English observers of Mars 
call it Dawes' Snow Island. On the other hand, I have often seen it 



168 



169 



as yellow, or even dark red, when near the central meridian. 1 It 
was shown as bright near the edge of the disk by Galle as early as 
1839. Dawes was struck by its brilliancy between 1852 and 1865, 
finding that it gave him the impression of an enormous mass of 
snow, and that in 1862 it was as brilliant as the polar cap. In 1856 
Webb, and in 1864 J. Phillips, also drew it as very brilliant. From 
1879 to 1890 Schiaparelli again sometimes observed it as dazzling 
as the southern snows, and this has been confirmed many times 
since then-among others by myself from 1894 to 1928 (Figs 24, 
25, 92 and 99). At the perihelic oppositions of 1892, 1909 and 
1921, I never found Argyre brilliant near the edge of the disk. 
However, it reappeared as very white in December 1928. This 
island is presumably an elevated plateau upon the planet. 

A brilliant projection was observed on the terminator at Argyre 
by Stanley Williams on 18 August 1894. Gledhill noted another 
projection on 24 January 18'99. 

horarum Promontorjum (S, 1877). This is the name of the 
pointed cape at the N of Argyre (Fig 67). 

charttum promontorium (S, 1877). Name of the SW cape of 
Argyre. 

NEREIDUM fretum. This is the sea-arm separating Argyre from 
Ogygis Regio (Fig 67). It was first accurately shown by Schiapar- 
elli in 1877. 

CAMPI phlaegrl Brown patches following Argyre, and which 
I have observed from Meudon. That of 1909 was small, very com- 
plex, knotty and veined (e = 11°); those of 1911, seen to the SW 
of Argyre, were more extended, and in the form of a U (e = 68° ), 
sometimes losing their brown colour because of the presence of 
yellow clouds. In 1924 Pease drew a vertical shading here; he was 
using the Mount Wilson 2 m- 57 reflector. This brown colour is 
probably not permanent. 



170 



mare erythraeum (S, 1877). This was the name given by the 
Milan astronomer to the immense sea containing the red archi- 
pelago which extends from Hellespontus to Thaumasia. I have 
found it more convenient to limit the name to the inland sea to 
the N of Argyre. The intense greyness of this region was shown on 
HerscheFs drawings made as early as 1873. Trouvelot, in 1877, 
showed inequalities of tone here, and these were confirmed by 
Stanley Williams in 1898-9, Molesworth from 1900 to 1903, and 
myself, among others, in 1909 and 1911. The colour here, grey to 
Schiaparelli, appeared bluish-grey to Molesworth from 1896 to 
1903 (e = 60° to 210°) and chocolate brown to Lowell in 1903 
(e = 197°). With m -83 it seemed to me to be pure green between 
1909 and 1926 (e = 309° to 64°); it gave the appearance of 
prairies broken by thick, darker woods (Figs 68 and 80). 

Schiaparelli believed that his mare Erythraeum was veiled by 
clouds in 1862, and he himself saw it darkened in 1877 by atmos- 
pheric veils of vast extent. 

VULCAN! PELAGUS. This is the W part of Pandorae Fretum; it 
goes up toward the SW. Schroeter drew it in 1798, Beer and Maed- 
ler in 1830. The inclination toward the SW is evident on the excel- 
lent sketch made in 1862 by Banks, a most skilful observer, using 
a small m 095 refractor; it is also recognisable on the drawings 
made by Trouvelot, the Henry brothers, Terby, Dreyer and Green 
in 1877, Boeddicker in 1881-2, Barnard in 1892, Maunder and 
Campbell in 1894, and myself in 1909 (Fig 26). In 1909 the incli- 
nation was clearly photographed by Hale and Barnard. I again saw 
this appearance in 1926, and it was also shown on Hubble's photo- 
graph. Vulcani Pelagus was green in 1909, 1924 and 1926 as seen 
from Meudon. 

In 1862 Lassell drew several sombre streaks here, and I found 
some large knots in 1924, when the colour of the Mare always 
appeared greenish. 



171 



SEXTANTTS depressio. Sombre part of the Vulcani Pelagus, near 
Pandorae Fretum. I observed it from Meudon in 1911, 1924 and 
1926. 

OCTANTIS DEPRESSIO. This is another dark spot of the Marc Ery- 
thracum, which I noted in 1924 and 1926, to the right of Sextan- 
tis Depressio. 

aquarji depressio. Dark spot which 1 observed with the m 83 
in 1924 in Vulcani Pelagus, to the NE of Argyre (Fig 67). 

iani fretum. This is the 'Canale di Dcucalione' of Schiaparelli 
in 1879, separating Deucalionis Regio from the continent. Schroe- 
ter represented it in 1798, Kunowsky in 1821. It is rather light in 
the sketches by Beer and Maedler, very intense in those made by 
Secchi. Dawes and Green drew it as too broad. To Schiaparelli in 
1877, it was not sharp; in 1879 he saw it as very black; in 1881-2, 
less so; in 1890, double. From Meudon I often see it darker than 
Deucalionis Regio (Fig 43), and this is also shown on the photo- 
graphs taken since 1909. 

iani SINUS. Bay formed by Iani Fretum at its right extremity. 

MARGaritifer sinus (S, 1877), This great gulf at the W of the 
Sinus Meridian i, with its blunt point to the NE, is first recognis- 
able on the sketches made by Herschel in 1 783. Tapered by dif- 
fraction in instruments of ordinary size, it appears as a sort of 
square to the N when seen under high magnification (Fig 68), and 
this is how it was shown on the beautiful photograph taken by 
Hale in 1909. The W coast is variable on the side toward Hydaspis 
Sinus, and in 1879 Schiaparelli was astounded to see the gulf re- 
duced in size; at this time Niesten showed it truncated to the N. 

Margaritifer Sinus has diffuse borders, contrasting with the 
clear-cut coasts of the Sinus Sabacus, and it is almost always less 
dark than the Sinus Meridiani. This is shown on drawings made by 
Beer and Maedler as early as 1830. Among the rare cases in which 
it has appeared as sombre as the Forked Bay may be cited the 
aspect described by Secchi in 1858 and Schiaparelli in 1877. A 






sketch by Herschel in 1783 shows it even blacker, but this is prob- 
ably due to an observational error or an opitcal illusion. To me it 
was dark from 1900 to 1903. With good images, the m '83 always 
shows the Margaritifer Sinus as definitely green (e = 309° to 71°). 




Fig 68 Margaritifer Sinus, uitli Bm and Pyrrhte Regio, on 22 September 
1924. (o m -8j refractor) 

From Milan, in 1890, Deucalionis Regio seemed to be joined 
on to Pyrrhae Regio, an aspect due to the presence of Martian 
clouds. At the time of the great pallor of 1909, which lasted for 
several weeks, and made Mars look lemon-yellow in colour, the 
Margaritifer Sinus was less affected than Sinus Meridiani, accord- 
ing to the observations which I made from Juvisy with Flammar- 
ion's m- 24 refractor and my own m, 216 reflector. On 29 June 
1922, G. Fournier and Hudclot saw it strongly indented and dim- 
inished to the NE, due to the effects of yellow clouds; and on 6 
July they saw it white on the terminator. On 18 January 1925, 
with the great refractor, I saw a projection on the terminator here, 
due to orange cloudy masses hovering above the gulf. 

HYDASPIS SINUS. In the second half of the nineteenth century, 
the W coast of the Margaritifer Sinus, which in 1830 had had its 
present-day appearance, underwent a strange transformation 
which lasted for at least twenty years. Secchi's drawings of 1858 
establish that there was then another gulf, sombre and pointed, at 



172 



173 



the mouth of Schiaparelli's Hydaspes; it was just as important as 
the Margaritifer Sinus (Fig 102). It was confirmed in 1862 by 
Lassell and Lockyer, in 1864 by Kaiser and Dawes, and in 1871 
by Lehardelay and Gledhill. Subsequently the indentation dim- 
inished, and in 1877 the drawings by Dreyer and Schiaparelli 
show it as far less marked. In 1879, as seen from Milan, it was re- 
duced to a harbour, and it was still seen in this form in 1892. This 
is also how Cerulli observed it in 1899, and how Hale photo- 
graphed it ten years later. Since 1909, with the m, 83, all I have 
been able to see here is a slight concavity on Chryse (Figs 68 and 
103). 

PYRRHAE REGIO (S, 1877). Long island, shaded in half-tone, 
thin and convex to the SW, rising above Aromatum Promontorium 
in a giaceful curve before losing itself above the Deucalionis Reg- 
ie Pyrrhae Regio was vaguely indicated on the map drawn by 
Beer and Maedler in 1838 and on the 1862 drawings by Lockyer 
and Lord Rosse's observer as well as those made in 1864 by Kaiser 
but it was not named until Schiaparelli christened it in 1877, In 
1892 Barnard and Hussey represented it as reasonably broad, and 
at this time Campbell found it clear to the NW, patchy elsewhere. 
It again appeared arched and pale on the 1909 plates by Barnard 
and Hale. I observed it beautifully in 1924 and 1926, when it 
seemed to be curvilinear; the reduced diffraction in the great tele- 
scope showed it to be thin (Fig 68). 

This island is extremely smoky, and is a little less bright than 
the floors of the adjacent seas. Schiaparelli found it yellowish -grey 
or grey; in 1924 and 1926 it seemed to me to be simply grey, with 
a tint of blue. 

Pyrrhae Regio sometimes whitens near the limb, as was noted 
from Milan in 1881-2, but this phenomenon is very rare. 

eos. The NW part of Pyrrhae Regio is the brightest area, 
though it is still shaded; this is the region which I have named Eos. 
It is vaguely shown, attached to the continent, on Secchi's draw- 

174 









ings of 1858, and on those of Lockyer in 1862, Kaiser in 1864, 
Dreyer in 1877 and Boeddicker in 1881-2; it is better drawn on 
the sketches by Barnard, Hussey, Campbell, Schaeberle and Miss 
Russell in 1892, where it is shown more or less separated from 
Chryse. Campbell represented it as less marked in 1894. From 
Meudon, in 1909, I saw it very easily; it was isolated, irregularly 
oval with indentations to the N, and elongated along the parallel. 
It was smoky yellow in colour, fading away to the S in Pyrrhae 
Regio. In 1924 I saw it less well (Fig 68). At this time, Hubble 
photographed it as patchy with the 2 m -57 reflector, and Pease 
using the same instrument, drew it as attached toward the E to 
Aromatum Promontorium. At this time Bidulat de PIsIe noted it as 
extended. In 1926, from Meudon, it was well marked. 

arsinoes depressio. Sombre band of the Mare Erythraeum, 
skirting Pyrrhae Regio to the SW. I saw it violet from Meudon in 
1924 (e = 350°) and in 1926 (e ■ 6° to 48°). 

aurorae FRETUM. Channel separating Eos from the continent 
(Fig 68). Schiaparelli drew it from 1879 to 1888, and recorded it 
double in 1890. Barnard, Campbell, Hussey and Schaeberle ob- 
served it as blackish in 1892. In 1909, with the m "83, I saw it 
clear and undulating to the S, diffuse to the N, and bluish-greenish 
in colour. 

aurorae sinus (S, 1877). This second great golf, lying to the W 
of Margaritifer Sinus, but with a more rounded coast, is shown on 
Herschel's sketches of 1777. From 1830 to 1837 Beer a.id Maed- 
ler observed it as elongated to the mouth of the Ganges, and it was 
not represented in its present -day form until Seech i did so in 
1858. Lockyer drew it more or less correctly in 1862, Kaiser more 
accurately from 1862 to 1864. In 1877 it appeared markedly ex- 
tended toward the Ganges, as is seen from the drawings made by 
Flamrnarion and the He.iry brothers, as well as those by Trouvelot 
(Fig 79), Terby, Schiaparelli and Green. From Milan, in 1879, it 

175 



seemed smaller. Trouvelot showed the N coast as broken in 1877. 
Aurorae Sinus does not seem to have altered in form since the ob- 
servations made by Schiaparelli in 1877. 







Fig 69 Aurora Sinus, with Capri Cornu, Jamuna Sinus and Gangis 

Sinus, in 1924, (o m -8j refractor) 

Aurorae Sinus is normally darker than Margaritifer Sinus, but 
not as dark as Sinus M^ridiani. In 1879, to Schiaparelli, it seemed 
as black as ink, which was very strange; in 1903, Lowell found it 
darker than the Sinus Meridiani. However, in general the intense 
darkness is confined to the N part, and is sometimes stopped to 
the S by a linear feature emerging from Aurea Chersonesus, and 
which I have named Capri Cornu. This is how it is shown in Fig 
69. In 1898-9 Cerulli noted a patchy structure in Aurorae Sinus. 
Schiaparelli saw it as grey; Molesworth bluish grey, from 1896 to 
1903 (e = 60° to 220°). To me, using the m -83 in 1909, it always 
appeared greenish (e = 8° to 14°); this was also the case in 1911 
(e = 47°). Phillips found it greenish in 1918 (e = 171°). In 1924 
I found it green until October (e = 282° to 10°), violet brown 
later (e = 30° and over). In 1926 it remained green to the S until 
10 November (e = 44°), and it was still green in 1928 (e - 93°). 
Thus it seems that around e = 30°, Aurorae Sinus changes from 
green to brown for some time. 

So far as clouds in this region are concerned, we have the fol- 
lowing cases: (1) The light pallor of the gulf which I noted from 
1896 to 1899; (2) the pallor of August to December 1900; (3) 
that of August 1909, which was, of course, particularly note- 



worthy; (4) the quick fading from 6 June to 24 November 1924, 
as seen from Meudon; and (5) its marked concealment in January 
1925. 

JAMUNAE SINUS. Small pointed indentation of the Jamuna, on 
Aurorae Sinus, It was drawn by Schiaparelli in 1879 and 1886, 
and seen by Danjon in 1920. I saw it beautifully with the m, 83 
in 1924 and 1926, when it was tapering and blackish (Fig 69). 
Traces of it may be seen on Hubble's photograph, mentioned 
above. 

GANGis SINUS. As has been noted in the description of Aurorae 
Sinus, the harbour of the Ganges was enlarged into a gulf between 
1830 and 1837, and also in 1877. At the end of 1879, Schiaparelli 
sometimes observed a small indentation, analogous to that of the 
Jamuna. In 1909, from Meudon and with excellent images, I could 
see no trace of it; but in 1924 I noted the small indentation men- 
tioned above (Fig 69). It was confirmed on Hubble's photograph, 
and was also present in 1926. 

nectaris SINUS. In 1924, I saw that the estuary of the Nectar 
remained green at the time when the seasonal green had turned to 
lilac brown (e = 30° ). 

CAPRI CORNU. From time to time, there may be seen a vague 
bright feature coming from the S of Aurea Chersonesus and pro- 
ceeding under Protei Regio toward Eos. I have named it Capri 
Cornu. It was drawn by Trouvelot and Schiaparelli in 1877, by 
Burton and Schiaparelli in 1879, by Holden in 1890, by Keeler in 
1892 and by Barnard in 1894. I saw it feebly in 1909 and clearly, 
particularly to the N, in 1911— and higher in 1924, when it ap- 
peared convex to the SSE and fell back, narrowing, toward Arom- 
atum Promontorium (Figs 69 and 80). At this time Hubble re- 
corded it photographically. It looked the same in 1926. On 8 
February 1929 it was joined, to the S, to Protei Regio. 



176 



177 



PROTEI REGIO (S, 1877). Small island with indefinite boundaries, 
very strongly smoky, difficult to see, and variable. It lies to the S 
of Aurorae Sinus, and Kaiser showed vague traces of it in 1864, In 
1877 Trouvelot, Schiaparelli and Green saw here a round patch, 
sometimes white, but in general a little less bright than the adjoin- 
ing sea. Niesten and Schiaparelli drew it in 1879. Subsequently it 
became brighter, as seen from Milan in 1881-2, and it was still 
visible in 1883-4. After a period of invisibility, it was drawn as 
extended by Hussey in 1892. It is not recognisable on the plates 
taken by Lowell and Lampland in 1907. I saw nothing here with 
the m '83 in 1909, when Lowell again failed to record it photo- 
graphically; in 1911, there was a slightly brighter spot in this 
position; and in 1924, I noted a half-tone which did not appear to 
be very sharp (Fig 80), confirmed by Hubble 's photograph. The 
same pallor was seen in 1926 from Meudon; but in 1928-9 Protei 
Regio was bright, extended and easy. Schiaparelli called it pale 
yellow in 1883-4. 

depressio erythraea. Extended sombre patch, lying to the N 
of Argyre I (Figs 67 and 80). Schiaparelli described it as particu- 
larly black. In 1909, from Meudon, I found it dark green. In 1911 
I saw it again; in 1924 I noted it as sombre and green up to 22 
September (e = 350°), but on 28 September (e = 353°) I judged 
it to be definitely lilac-brown, an observation soon confirmed by 
QueViisset. It was of the same colour as Arsinoes Depressio, the 
sombre streak going toward Aurorae Sinus. This changeable patch 
was well shown on Hubble 's photograph. It was still visible in 
1926. 

ogygis regio (S, 1877), This is a feeble half-tone, forming a 
variable island to the W of Argyre I, and less luminous than it. The 
shading of Ogygis Regio is easily recognisable on a drawing by 
Iiais in 1860, and it is unmistakable on the drawings made by 
Lockyer in 1862. In the latter year, Lassell and Kaiser joined it on 
to Argyre I, as did Trouvelot in 1877. Green at this time saw it as 
a very feeble half-tone. It was better shown by Schiaparelli 






from 1877 to 1882. Hussey also drew Ogygis Regio in 1892, and 
Lowell and Lampland photographed a strong shading here in 
1907. To me, at Meudon in 1909 and 1911, it did not seem well- 
defined, but it could be seen better in 1924 (Fig 80); at this time 
Hubble photographed it, while it was also drawn by Bidault de 
PIsle. In 1926 it was always confused. 

Trouvelot painted Ogygis Regio as red in 1877, and to me in 
1924 it was brick-red. 

In 1881-2 Schiaparelli found that land sometimes whitens when 
seen obliquely; I have confirmed this on more than one occasion, 

BOSPOROS GEMMATUS (S, 1877). This channel, sometimes som- 
bre, separating Ogygis Regio from Thaurnasia (Fig 80) was drawn 
by Hcrschel as early as 1783, and by Schroeter in 1798. Beer and 
Maedler, in 1830, showed it accurately. In 1877, Trouvelot and 
Cruls represented it as moderately dark, and on the 1907 photo- 
graph by Lowell and Lampland it was again paler than Aurorae 
Sinus. It appeared triple from Meudon on 8 February 1929. Lock- 
yer recorded it as green in 1862 (e = 20°); I confirmed this in 
1909 (e = 1 1°), but in 1924 I found that the strait, which had pre- 
viously been green, turned progressively to brown, from S to N, 
from mid-August (e = 324°); the discolouration was complete by 
19 September (e = 347°). On 8 February 1929, the triple mass 
was lively chestnut-colour, with a magnification of 540 on the 
great m "83 refractor (e = 1 13° ). 

In all probability, Sccchi saw this channel interrupted by clouds 
in 1862, and once, in 1877, Green saw it cut in half. I found it 
pale in 1894, obliterated' in August 1909, and sometimes invisible 
from Meudon in 1924. 

DELPHINi PORTUS. Very dark patch touching Thaurnasia, to the 
S of Nectar. On 6 October 1909, from Meudon, it appeared to me 
to be black and round, like the shadow of a satellite of Jupiter; 
this was also noted by Crouzel with the Toulouse m '38 refractor. 
With the m "83 it was less evident in 1911, 1924 (Figs 80 and 83) 
and 1926 (Fig 84). 



178 



179 



phrixi regio. Dark half-tone, touching Thaumasia to the SE. 
It was observed by Campbell in 1894, by Rheden in 1898-9, and 
by myself from Meudon in 1909. Crouzel also saw it. To me it 
appeared very vague in 191 1 and 1924 (Fig 80). 

In 191 1, for the first time, I saw Phrixi Regio slightly whitish 
after sunrise. 

coracis TORTUS. Another very dark patch, touching Thaumasia 
to the S. It was drawn by Lassell in 1862, by Molesworth in 1896- 
7, by Lowell in 1907, and by me in 1909, when, like Delphini 
Portus, it appeared round and black in the m> 83. Crouzel also 
saw it at this time. In 1911 it seemed to me to be feeble; in 1924, 
I saw it dark (Figs 80 and 83). It looked the same in 1926 (Fig 84) 
and it was sombre as seen from Meudon in 1928. 

depressio PONTICA. Extended shading to the SSW of Coracis 
Portus. It is shown on a drawing made by Schroeter in 1798, and 
on one by Lassell in 1862. Schiaparelli drew it in 1879. With the 
m '83 it was striking in 1909; it was photographed at this time by 
Lowell. I again saw it in 1924 (Figs 80 and 83), as did Pease with 
the 2 m * 5 7. 1 noted it once more in 1926 (Fig 84). 

chrysokeras. A horn in half-tone, issuing from the summit of 
Thaumasia toward the SSW. Rosse's observer showed traces of it 
in 1862. It was well represented by Hussey and Barnard in 1892 
and by Barnard in 1894. In 1909, from Meudon, it seemed to me 
to be broad at the base, narrowing irregularly toward the top. It 
was photographed by Lowell in this year. In 1911, 1924 and 1926 
it was confused in the m "83 (Figs 80, 83 and 84). 

In May 1888, Schiaparelli noted a white marginal patch near 
longitude 106°, latitude -51°, near Chrysokeras, which seems to 
me to whiten sometimes when seen obliquely. It showed as dim 
white in 1909 and 1924. 



bosporium PROMONTORIUM. The S point of Chrysokeras. 



BATHYs PORTUS. The third sombre patch touching Thaumasia 
to the SW, at the bottom of Aonius Sinus. Holden and Douglass 
drew it in 1894, Lowell in 1896 and 1907. I observed it in 1909, 
with the m '83, as black and circular, like the shadow of a sat- 
ellite of Jupiter, and very like Delphini Portus and Coracis Portus. 
In 1911, 1924, 1926 and 1928 it seemed to me to be much less 
intense (Figs 80, 83 and 84). 







180 




Fig jo Sods Lacus, blackish, with the very well-developed Aonius Sinus, 
on 2J September i8jy, according to Flammarion. fo m -20 refractor) 



aonius SINUS (S, 1877). This greai gulf, which follows Thau- 
masia, underwent a curious transformation in 1877, when it be- 
came pointed and blackish, though it has since reverted to its 
normal appearance. Vaguely indicated by Herschel in 1783 and 
Schroeter from 1785 to 1802, it was shown blunted by Beer and 
Maedler from 1830 to 1841, Kaiser, Lockyer, J. Phillips, Knott, 
Lassell and Rosse's observer in 1862, and again by Kaiser in 1864. 
But in 1877 Flammarion, who was an excellent observer, precise 
and judicious, saw Aonius Sinus as very sombre or blackish; so did 
the Henry borthers, Trouvelot, Schiaparelli, Terby, Holden and 

181 



Green, It seemed to penetrate deeply into the continent, broaden- 
ing into a trumpet-shaped feature and debouching into the Pharsis 
(Figs 70, 79 and 81), The drawings by Schiaparelli (Fig 71),Nies- 
ten and Burton in 1879 indicate a slight tendency to return to 
normal. In 1881-2 and 1890 the aspect was the same as seen from 
Milan. However, in 1892 Hussey, Barnard, Campbell and I, using 
an m, 108 telescope, showed a blunted patch here; 1 again drew it 
in this form in 1894 with Campbell, Schacberle, Lowell, Douglass 
and Stanley Williams. In 1907 Lowell and Lampland photograph- 
ed it. I again saw it from Meudon in 1909 (Fig 72), and it was 
confirmed by Lowell's plates. I subsequently identified it with the 
m -83in 1911 and 1924 (Figs 82 and 83). 




Fig 71 Schiaparelli, 1879 fo m -2i8 refractor) and Fig 72 Antoniadi, 

1909 (o m -83 refractor). Changes in Aonius Sinus, which appeared highly 

developed in T877-9 

Aonius Sinus is dark, as was represented by Herschel and by 
Beer and Maedler, and it appeared sombre from Meudon in 1909. 
Lockyer saw it green in 1862 (e = 20°), as did I, with the m -83, 
in 1909 (e = 8°); but in 1924 I found that it was greenish before 
9 August (e = 322°) and subsequently became brown. In 1926 it 
was at first green (e = 337° ) and became brown after 29 Septem- 
ber (e = 20° ). In 1928 it was again green (e ■ 93°). 

According to my observations from juvisy in 1894, the gulf was 
veiled by yellow clouds; it was invisible at the beginning of Sept- 
ember 1909, and seemed feeble in 1914. On more than one occa- 
sion in 1924, Bidault de l'lsle noted it as pale. 

182 




DEPRESSIONES AONiAE. Dark patches on Aonius Sinus, drawn 
vaguely by various observers such as Kaiser, Trouvelot and Cmls. I 
have seen them clearly in the m '83; they were green in 1909 (e ■ 
8°), brown as seen from Meudon on 10 August 1924 (e = 323° 
and greater). They appeared as green on 23 July 1926 (e = 337° ), 
and later as brown (e = 20° ). These are the main dark patches, 
according to my observations of 1909. 

ARGUg DEPRESSIO. Extended sombre patch to the S of Bathys 
Portus. 

DORADUS DEPRESSIO. Large but less dark patch, to the SW of 
Bathys Portus. 

crateris depressio. Another sombre patch, to the S of Dorad- 
us Depressio. 

piscis depressio. Dark patch at the entrance of Palinuri Sinus. 

thymiamata (S, 1877). Continental region of variable intensity, 
bounded by the lani Fretum to the S, the Margaritifer Sinus and 
the Oxus I to the W, and the Gehon I to the E. Maedler showed it 
shaded in 1841, as did Niesten in 1879, Schiaparelli in 1881-2, 
and myself with the m, 83 in 1911. However, Danjon drew it as 
brighter than Eden in 1920, and I confirmed this in 1924. Thymi- 
amata seemed red to Seech i, orange-yellow to Schiaparelli, orange 
to Boeddicker. In 1888, from Milan, it seemed dull red and 
yellowish-brown. Gale found it reddish and I noted it as rose in 
1924. Holden always described it as red. Thymiamata often 
whitens when near the edge of the disk. This was shown as early 
as 1856 on a drawing by Brodie. 

ARAM. This is the S part of Thymiamata which is normally 
brighter than the region to the N. Boeddicker confirmed this as- 
pect in 1881-2, as did Molesworth from 1900 to 1903, McEwan in 

183 



1915-6 and Briault from 1916 to 1918. The boundary between 
the two half-tones marks the site of the Cantabras. In 1924, this 
S part of Thymiamata appeared bright rose to me with theO^'SS, 
and it was the same in 1926 and 1928. 

Schiaparelli noted a white patch in this area in 1881-2, and 
white clouds covered up Aram on 28 and 29 June 1922, as noted 
by G. Foumier and Hudelot. Aram often whitens when seen ob- 
liquely, at the same time as Thymiamata. 

AUREUM CORNU. The Milan observer gave the name of 'Cornu 
d'Oro' to the promontory leading away from the SSW of Thymi- 
amata. 2 

Oxta palus (L, 1894). To the N of Margaritifer Sinus there is a 
sombre, isolated lake, clearly drawn by Schiaparelli in 1877 and 
1888. Lowell observed it in 1894, Cerulli, Douglass and Rheden in 
1898-9, Molesworth from 1900 to 1903. Lowell reobserved it as 
very small in 1907. From 1909 to 1914 G. Fournier drew it in 
elongated form SW-NE, which is correct; as did Briault between 
1915 and 1918. I noted it as blackish, also elongated SW-NE, in 
1924 (Fig 43); this was also recorded by Graff with an m -60 
refractor and confirmed photographically by Hubble. The same 
object was seen from Meudon from 1926 to 1928. Cerulli once 
saw Oxia Palus surrounded by a rose-coloured aureole. 

oxu. Shaded area, bounded by the Gxus 1, the Indus and the 
Jordan. Galle was the first to see it; in 1839 he recorded it as grey- 
ish. Secchi, Green, Molesworth, the Fournier brothers, Briault and 
I have confirmed it with certainty, and it was also shown on 
Hubble's plate. 

CHRYSE (S, 1877). By this name Schiaparelli indicated the vast 
continental region bounded by the Aurorae Sinus to the S, the 
Ganges to the W, the Nilokeras and the Niliacus Lacus to the N, 
and the Indus with the Margaritifer Sinus to the E. But as the W 



184 



half is shaded, it seems more convenient to separate it, and this I 
have done. In 1898-9 Kempthorne drew attention to the fact that 
the N part of Chryse is very lightly smoky, and I also saw this in 
1909, from Meudon. Maedler saw this arid desert as definitely red, 
Holden very yellow, Lowell red, Gale reddish, Eddie very ochre, 
Quenisset brick red. It seemed reddish rose to me in 1924. 

Yellow clouds often cover Chryse. In 1877 Trouvelot observed 
a white patch 10° long in the south of the area. Moreover, Chryse 
very often whitens near the limb, as was rocorded by Schiaparelli 
in 1877; 1 have sometimes even observed it as glittering white. 

On 26 May 1903, Lowell recorded a brilliant projection from 
the terminator in the N part of Chryse. 

aromatum promontorium (S, 1877). This beautiful rounded 
cape at the S of Chryse was first recorded by Herschel in 1783. 
With the m '83 I always see it as a projection (Fig 68), and it has 
not changed much over the past 140 years. 

hydrae palus. Small bay in the SW part of Chryse. Maedler 
may have glimpsed it in 1841; Holden observed it clearly in 1890. 
To me, from Meudon, it seemed very broken up in 1909, but 
flowing in 1911 and 1924 (Fig 101). 

xanthe. This is the western, smoky part of Chryse. The shaded 
outline is shown on Maedler's drawings made as early as 1841. 
Kaiser saw it again in 1864, Niesten in 1879; it has since been re- 
corded by many observers. To me, with the m "83, it always 
appears diffuse and degraded to the E (Fig 101), and Mme G. C. 
Flammarion drew this aspect well in 1922. The existence of this 
grey area has been confirmed photographically. Maedler saw here 
a pure red colour, Boeddicker a reddish brown in 1884 (e = 152°), 
Graff brown in 1911 (e = 65° ), and I saw a clear chestnut tint in 
1911-2, 1924, 1926 and 1929 (e = 47° to 87°, 304° to 31°, and 
1° and greater). This brownish colour is evidently permanent in 
these regions. 

185 



Xanthe sometimes whitens under oblique viewing, but less so 
than Chryse. 



LUNAE lacus (S, 1879), Lying to the W of Xanthe and to the N 
of the Ganges, this great lake, as extensive as Moeris Lacus, was 
vaguely indicated on the 1777 sketches by Herschel. Beer and 
Maedler observed it, more accurately from 1837 to 1841, and once 
even drew it elongated along the parallel of latitude, which is 
the true form. Schiaparelli recorded it as double from 1879 to 
1890, except in 1886. To me it appeared vast, lenticular and very 
degraded toward the edge in 1911-2 and 1924 (Fig 73). In the 
latter year I saw two condensations there, and the photographs 
showed the lake extended and diffuse. It was still oblong, but 
rather pale, in 1926 and 1928. In general, its intensity is not gVeat, 
but Trouvelot found it blackish in 1888. The colour of Lunae 
Lacus was noted as reddish from Milan in 1883-4 and 1888 (e = 
220°) and cherry-red by Cerulli in 1898-9 (e = 133°). To me it 
appeared chestnut-brown in 1911-2 (e ■ 47° to 87°) and also in 
1924, when Baldet and Mohr confirmed this tint (e = 347°). The 
aspect was the same in 1926 (e = 20° to 64°) and in 1928-9 (e = 
93° to 129°). 

A pale inland lake, such as this, is, not surprisingly, often cloud- 
covered, particularly at perihelic oppositions; this is why nobody 
drew it in 1862. It was scarcely seen in 1877, and was only glimps- 
ed in 1909 even with the m, 83. 




Fi S 73 Luna l-acus in K/24. (O m -8j refractor J 



186 



insula sacra (S, 1879). Optical island, glimpsed by Schiapar- 
elli near Lunae Lacus at the time of its doubling in 1879. 




Fig 74 Barnard, 1892 and Fig 75 Antoniadi, 1909. Aspects of Juventa 
Pons, in large instruments 

Juventae fons (S, 1877). This remarkable little blackish patch 
on the Ganges, almost equal in area to our Lake Huron, was 
shown on a drawing made by Lassell in 1862. Green glimpsed it, 
though not clearly, in 1877; Schiaparelli saw it as 'an inland lake, 
very small and round'; its diameter 'cannot exceed 3° \ Invisible 
from Milan in 1879, it reappeared in 1881-2, in the form of 'a 
large black point, circular', 3° in diameter. The lesser diffraction 
in the m- 91 refractor showed Juventae Fons as larger and more 
sombre to Holden in 1890. Hussey drew it in 1892 as round and 
very dark, Schaeberle smaller, Barnard elongated in the same sense 
as the Baetis (Fig 74). Campbell and Holden saw it again in 1894. 
Millochau, in 1900-1, also drew it as elongated, and Lowell and 
Lampland succeeded in photographing it in 1907. The Fournier 
brothers drew it as small and blackish in 1909, 1911 and 1914, as 
did Briault between 1915 and 1918. From Meudon I saw it large, 
beautifully round and blackish, subtending almost 5° and obeying 
the laws of perspective, in 1909. It was confused, though dark, in 
19 U; smaller and less evident in 1924 (Fig 80), 1925 and 1928-9. 
It was then elongated in a N-W direction, as had been the case in 
1892 and 1900-1. Its extremely sombre tint struck me vividly in 
1909; its colour was then green indigo, almost black. 

Naturally, this little lake is highly prone to concealment below 
Martian clouds; this was observed by Schiaparelli in 1881-2 and 

187 



confirmed by myself in 1909, 19U-2, 1924 and 1926, 

ophir (S, 1877). Very barren continental region, bounded orig- 
inally, by the Agathodaemon to the S, the Chrysorrheas to the W 
and the Ganges to the E. From 1879 to 1882 Schiaparelli noted it 
as white to the SE, and I confirmed this in 1926. With the great 
refractor, I almost always see it whitish to the E. 

Ophir sometimes whitens under oblique lighting, as Schiaparelli 
noted in 1879. 

candor. This is the brightest part of the original Ophir, along 
the Ganges. Traces of this whitish streak are found on an 1862 
drawing by Lord Rosse's assistant. Holden observed it without 
difficulty in 1877, Boeddicker and Schiaparelli in 1881-2. Subse- 
quently Barnard represented it in 1892 and 1894, as did Lowell 
and Douglass in the latter year. Rheden noted it in 1898-9, and 
Lowell and Lampland photographed it in 1907. I have almost 
always found it easily since 1909; whitish, sometimes glittering, 
from Meudon (Fig 75). It is notable that this patch, one of the 
most luminous on the Martian surface, is adjacent to juventae 
Fons and the blackish lakes of the Agathodaemon, the most som- 
bre on the whole planet. 

On 4 May 1903, Molesworth noted a white projection at the N 
of Candor. 

tithonius lacus (S, 1881-2). This is a nest of lakes to the SW of 
Ophir, antipodal to Moeris Lacus. Represented by Beer and Maed- 
ler in 1837 and 1839, Tithonius Lacus was seen by Kaiser and 
Lockyer in 1862, when Secchi recognised its W-form. Kaiten ob- 
served it in 1864; according to Schiaparelli, Dawes then drew 
it too large. Its complex structure was recognised by Hussey 
who, in 1892, drew six irregular lakes here, which I con- 
firmed from Meudon in 1909, 1911, 1924 (Fig 80) and 1926; 
these lakes are described below (Fig 76). Boeddicker saw a grey- 
ish-orange colour here in 1881 (e = +90°); Keeler greyish red, very 

188 






different from the grey of Solis Lacus, in 1892 (e = 341°); Doug- 
lass green in 1898-9 (e =tl20°); myself grey-blue greenish in 
1909 (e = 8°). In 1924, the two dark lakes to the E seemed to me 
to remain grey (e = 301° to 30°), but the other four were a strik- 
ing chestnut red after 17 September (e = 346°). They were chest- 
nut again in 1926 (e = 20° to 44° ) and also in 1928-9 (e = 1 13°). 



i**"-*^ 


'A. 


. 






s 


'*, 


... || 
1 






^» 


l 








-km. 


IODU 




e.M4 




' •' 





Ftg 76 Tithonius Lacus, sextuple, in igotj. (o m -8;} refractor) 

The group of lakes was extremely pale in 1877; Trouvelot and 
the Henry brothers did not see them in that year, while Schiapar- 
elli (Fig 81), Flammarion (Fig 70), Dreyer and Green showed 
them as small and very feeble. They were more easily distinguish- 
able in 1879, according to Green and Niesten, but not so clear 
from 1883 to 1886, according to Schiaparelli. I did not see them 
in 1900-1, but saw them as intense in 1909; then less marked in 
1911, 1924 and 1926, and very pale in 1928-9. 

cm lacus. This is th^ easternmost of the six principal lakes 
making up Tithonius Lacus. Like the sombre Agathodaemon, it is 
almost always blackish, and is 3° in diameter. In 1892 Hussey 
drew it as a small core on the Agathodaemon, and this was con- 
firmed by Schaeberle in 1894. Lowell observed it in 1907. To me, 
with the m "83 in 1909, it showed up as an indigo greenish-black- 
ish colour. Graff represented it in 1911. It then appeared to me to 
be less sharp, and this was also the case in 1924 and 1926. 

melas lacus. Second lake of the Tithonius Lacus, reckoning 

189 



from left to right. It is oval, measuring 6° by 5° , and its area is 
almost equal to that of our Lake Superior. Maedler sketched it in 
1837, Lassell in 1862, Schiaparelli in 1877, Burton and Niesten in 
1879. Then, in 1892, Hussey and Campbell saw it as a large con- 
densation on the Agathodaemon, as did Campbell, Holden, Schae- 
berle and Lowell in 1894. Rheden saw it again in 1898-9 Millo- 
chau in 1900-1. In 1909, from Meudon, I was astonished to see its 
beautiful oval form and its indigo-green, almost black colour. 
Graff saw it in 1911, though it then seemed to me to be less 
evident, and this was also the case in 1924, when Bidault dc l'lsle 
drew it clearly; subsequently it was pale in 1926, and again black- 
ish on 29 December 1928 and 8 February 1929. 

HEBES LACUS. The third lake, situated on the equator, is smaller 
and paler than the previous two. Hussey drew it round and poorly 
defined in 1892. It was again seen by Barnard, Campbell, Schae- 
berle and Lowell in 1894. From Meudon, in 1909, it seemed to 
me to be circular, pale and rather small. Indistinct in 1911, it 
appeared to me to be chestnut-red after the middle of September 
in 1924 (e =±346°) and also in 1926 (e = 6°). 

IUS lacus. The fourth of these lakes is comparable with Hebes 
Lacus. Hussey saw it as round and blackish in 1892. Holden ob- 
served it as a black point, Barnard as indistinct. In 1909 it seemed 
to me to be of a darker tint than Hebes Lacus, and in 1924 and 
1926 the same colour as Hebes Lacus. 

ECHUS lacus. The fifth lake resembles the third and fourth. In 
1892 it appeared round and black to Hussey. Barnard and Schae- 
berle observed it as indistinct in 1894, Campbell and Holden as 
joined with Noctis Lacus. I found it difficult to distinguish in 
1909. In 1924 and 1926, with the m ' 83, I saw the Echus Lacus 
as the same in appearance as the two preceding lakes. 



NOCTis lacus. The sixth component of Tithonius Lacus is simi- 



190 






lar to the preceding three. Hussey drew it as black, and elongated 
along the parallel of latitude, in 1892; Campbell could not separ- 
ate it from Echus Lacus, and nor did he in 1894. In this year 
Barnard, Schaeberle and Douglass drew it round and black; Hold- 
en did not separate it from Ius Lacus and Echus Lacus. Lowell 
recorded it as double in 1907. From Meudon in 1909, 1924 and 
1926 it seemed to be similar to the three preceding lakes, but 
rather larger than any of them. 

AUREA CHERSONESUS (S, 1877). According to Schiaparelli, a 
variable feature, almost an island, to the NE of Thaumasia. It was 
clearly indicated by Beer and Maedler in 1830, when it was of 
considerable extent. Lassell, Kaiser and Lockyer drew it as well- 
developed in 1862, Kaiser and Dawes as even larger in 1864. In 
1877 it was enormous; the drawings made by the Henry brothers, 
Trouvelot (Fig 79), Flammarion (Fig 70), Cruls, Niesten, Terby, 
Dreyer, Green, Harkness and Schiaparelli (Fig 81) show it as truly 
vast at this time. In 1879 it was still of abnormal size, according to 
Schiaparelli (Fig 77), Niesten and Burton. In 1881-2 the drawings 
of Boeddicker and Schiaparelli show it diminished, and this be- 
came more marked as seen from Milan in 1883-4. 'This peninsula, 
formerly so beautiful, has been considerably reduced, or at least 
transformed', wrote Schiaparelli in 1890. 3 The drawings by Hus- 
sey and Barnard made Aurea Chersonesus of normal size in 1892, 




Fig 77 Schiaparelli, 1879 (o m -2i8 refractor) and Fig 78 the author, 
igil (o m -83 refractor) AUREA CHERSONESUS, enormous in 1879 



191 



and my observations since 1894 confirm this (Fig 78), as do the 
photographs taken by Lowell in 1907 and 1929 and Hubble in 
1924. 

Aurea Chersonesus appeared greyish from Milan in 1890, 
though in 1926 it was whitish. 

thaumasia FOEiix (S, 1877), This vast land, as big as half Aust- 
ralia, surrounds Solis Lacus. It is in part somewhat smoky, and its 
outline is not circular-as it was formerly drawn-but has a very 
irregular coast and a point to the S. It was first shown on a sketch 
by Herschel in 1783, in which the upper border is clear. In 1830 
Beer and Maedler represented only the SE side; Secchi did not 
succeed in recording it clearly in 1862, and believed that he had 
distinguished a spiral structure, indicating 'a great squall on 
Mars'. 4 However, Kaiser defined it more accurately and made out 
its elongated shape in a S to W direction. In 1877 Flammarion, 
Trouvelot and SchiapareUi saw it as round (Figs 70, 79 and 81). 
Barnard, Campbell and Hussey showed it considerably reduced in 
1892; the combination of diffraction on the contour of Thau- 
masia and on that of Solis Lacus made it appear broad in small 
telescopes, narrow in large ones. In 1909, with the m "83, I was 




tig '79 lhaumasia Fwlix, rounded, and the oval Solis Lacus, blackish 

and elongated in a north-south sense, with the highly-developed Aouius 

Sinus and Phasis in 1877, according to Trouvelot. (o m -j8 refractor) 



192 








Fig 80 Chart of the region of Thaumasia and Solis Lacus in 11)24. 
(o m -8j refractor) 

able to see indentations toward Delphini Portus, Coracis Portus 
and Bathys Portus; then a convexity toward Phrixi Regio, and a 
point to the SW. The photograph taken at this time by Lowell 
confirmed these results in general, and I found the same aspect 
again in 1911 (Fig 82). In 1924, however, Bidault de 1 *I s ler noted 
changes here, and I con firmed that the land-mass above the Nectar 
had become thinner (Fig 80); it had the shape of a bear's head 
seen in profile, and this thinning was still marked in 1926 (Fig 
84). 

The S part of Thaumasia is considerably shaded, as was first 
indicated by Kaiser in 1862. To Terby, in 1877, the half-tone 
extended from the Nectar to the Bathys, and I confirmed this in 
1909. With the m *83, I saw in 1924 (Fig 80), 1926 and 1928 
that the greyest part of Thaumasia was the region to the E of the 



193 



Ambrosia. In 1879 Niesten, and in 1881-2, 1886 and 1890 Schia- 
ion noted it as red. From Meudon, I estimated it as coppery red, 
other observers have subsequently noted the same aspect. Lowell 
and Lampland's photographs of 1907 provide extra confirmation, 
except for the W part. However, in 1924 Thaumasia sometimes 
seemed to me to be brighter than the neighbouring regions. From 
Milan, Thaumasia was seen as yellow-brown; Mme G. C. Flammar- 
ion noted it as red. From Neudon, I estimated it as coppery red, 
rose in 1924, and a very strange ruby-carmine on 8 July of that 
year. 

Thaumasia sometimes appears yellow due to clouds. It some- 
times whitens when seen obliquely, especially when Mars is fairly 
distant from the Sun, as was noted by Schiaparclli in 1879. 

On 20 October 191 1, from Meudon, I saw two light whitish projec- 
tions from the terminator in this region, I noted a yellow salient on 
6 December 1924, and another on 8 January 1925. 

FEUS promontorium. Cape at the E of Thaumasia, which, with 
Baldet, I saw somewhat pointed in 1924. 
heiueum promontorium. Blunt cape at the S of Thaumasia. 
claritas. To the W of Solis Lacus there is a brighter part of Thau- 
masia, drawn by Barnard in 1894. In 1901 Attkins saw a very white patch 
here. With the o m> 83, in 1909, I saw a bright lemon-coloured area (Fig 
72), and this is identifiable on the photographs taken in 1907 by Lowell 
and Lampiand. V. Fournier drew it in 191 1 ; and in 1924, 1926 and 1928- 
9, from Meudon, I found that this part of the desert showed a brighter, 
rosy tint. 

nectaris fons (S, 1 877). Small condensation on the Nectar. Green and 
Dreyer noted a lake in these latitudes in 1877, seen as completely black 
by Schiaparclli (Fig 8t); but in 1879 Schiaparelii saw it only as an 
estuary of the Nectar, as Christie had done two years earlier. However, in 
1879 Burton noted the object as being isolated. From Meudon, in 1909, 
I saw a lake lying toward the E branch of the Nectar, and this was con- 
firmed by Crouzel. Pease recorded it in 1924 with the 2 m - 57 Mount 
Wilson reflector. 
taur: fons. This is another condensation on the Nectar, further to the 

194 



W. I found it striking in 1924 (Fig 80) and Pease drew it as pointed at this 
time. 

solis lacus (S, 1877). This enormous lake, in the middle of Thau- 
masia, has been nicknamed 'the Eye of Mars', and Maunder has com- 
pared its area with that of the Black Sea. I have found that it was first 
drawn by Maraldi in 1704. Beer and Midler saw it as round in 1830. In 
1862 Kaiser, with a larger telescope, was able to see its oval form, broader 
to the right and elongated along the parallel of latitude; Lockyer at this 
time saw it oblong in a WSW direction, and Lassell recorded it as more 
extended in the same direction. However, Secchi saw it elongated N-S, 
and so did that great observer Trouvelot in 1877 and 1894. In 1864 
Dawes confirmed Lockyer's results. The WSW elongation was greatly 
reduced in 1877, when it was studied by Flammarion (see the beautiful 
drawing: Fig 70), while Niesten, Harkness and Green showed it as 
feeble. Schiaparelii (Fig 81), Terby, the Henry brothers, Dreyer and 
Niesten draw it as circular. The E part of Solis Lacus was invisible at 
this time, and so was the Nectar, which is very puzzling. In 1879 Burton 
showed the Solis Lacus as elongated E \V, and double; Niesten drew it as 
oblong, Schiaparelii as round, Lohse as square! In 1881-2 Bced dicker, 




Fig 81 Schiaparelii, i8jj (o m -2l8 refractor) and Fig 82 Antoniadi, igu. 

(o m -83 refractor) 



195 



Niesten and Schiaparelli still saw it elongated E-W. It appeared in this 
form from Milan from 1883 to 1888; in 1890 Schiaparelli saw it pear- 
shaped, ^elongated WSW, and cut in two by a bright ligament — though 
at this time Holden saw it very extended, and elliptical E-W. In 1892 
Barnard, Campbell and Hussey drew it as large, and oblong toward the 
WSW. Barnard and Campbell saw the same aspect in 1894, when 
Schjeberlc showed it as triple. In 1898-9 Cerulli drew it double, as did 
Lowell in 1907; Lowell noted it as being made up of a large round spot 
to the right, preceded by a smaller one to the left, a little as Burton had 
shown it in 1879 — but the photographs taken by Lowell and Lampland 
showed it only in the form of a pear, oblong toward the WSW. In 1909, 
with the o m -83, I saw the Solis Lacus as strongly elongated in this direc- 
tion, as Quenisset had already pointed out; it was irregularly pear-shaped, 
with the broad tip to the right. This was confirmed by Lowell's photo- 
graphs, which I received later. The elongation seemed to me to be even 
more pronounced in 1911-12 (Fig 82), and this was confirmed by Graff. 
G. Fournier drew the lake as triple in 1913-4; Brian It, in 191 5-6, 
showed it as composed of two round spots, that to the right-hand side 
being the more important. Danjon showed the Solis Lacus as oval in 
1922. I again saw it pear-shaped in 1924, oblong toward the WSW, but 




F'g 83 (i9 2 4) anti Fig 84 (1926) Extraordinary change seen in Solis 

Lacus in 1926. Observations made when images were improved, near 

sunset. (o m -8j refractor) 



196 




reduced in size (Figs 80 and 83); this was confirmed by the photographs 
taken in the same year. Bidault de 1'Isle then noted that the Solis Lacus 
had changed, and had become double. Then, in 1926, 1 found it radically 
transformed. It was curved back toward the WNW, at a right angle to its 
original direction 5 (Fig 84). Using the o"'-83 1 found the same essential 
aspect in 1928-9; the lake was patchier, but still oriented NNW. 
Schiaparelli was right when he said: 'It is undeniable that the Lake of 
the Sun changes in form and size.' 8 

Moreover, the intensity is not always the same. Feeble in 1704, and 
presumably still weak from 1783 to 1800 in view of the fact that Hcrschcl 
and Schrceter did not draw it, it appeared very intense to Beer and 
Maedler in 1830, but it was paler from 1837 to 1839. Drawings made by 
Seech i, Kaiser, Lockycr and Lassell established that it was sombre in 
1862, but according to Kai'ser and Dawes it was weaker in 1864. Solis 
Lacus attained its maximum intensity in 1877; Flammarion and Trou- 
velot drew it black in this year (Figs 70 and 79), while Schiaparelli called 
it 'a strong black spot about \cf in diameter', 7 while Green described it 
as very sombre, always catching the eye before any other patch. In 1879 
it was still black as seen from Milan, and I. Ward also saw it as black and 
as sharp as the shadow of a satellite of Jupiter! From 1892 to 1924 I 
almost always found it rather pale, except in 191 1 ; but in 1926 and 1928 
it again became very dark, perhaps as much so as it had been in 1877. In 
1881-2 Schiaparelli noted that Solis Lacus was easier to see when near 
the limb than when on the central meridian, and I confirmed this in 1 894, 
when I found the lake always very pale near the centre of the disk, 
though once, for the fraction of a second, it appeared very dark and 
circular near sunset. 

Lowell showed regular nuclei in Solis Lacus in 1894. With perfect 
images in the o ni '83, from Meudon in 1909, I noted five regions which 
were darker than the central part, though of unequal tone — leading to a 
tendency to doubling in smaller instruments. Lowell saw the lake bluish 
black in 1896 (e = 89°). In 1909, to me, it appeared greenish grey or 
olive (e = 11 ); in 1924 I noted it grey until October, after which the 
colour turned clearly to a greyish brown (e = 30 )*, in 1926, it was at 
first a magnificent emerald green (e = 20 to 44 ), brown later (e = 64°). 



197 



This brownish tint was mentioned to me by Mile. Roumens, observing 
with the o m '83. In the same year Danjon saw it green and brown 
(e = 48 ). In 1928, it was violet brown as seen with the o">-83 (c = 93 ), 
and this was confirmed on 5 February 1929 by Mile. Roumens, Lyot and 
Bidault de 1'lsle with the Meudon refractor (e = 11 1°); but on 8 Febru- 
ary it seemed to me to remain brown to the SE, the NW part having 
become grey (e = 113 ). 

Naturally, Solis Lacus sometimes disappears beneath yellowish clouds. 
I found this to be the case at the beginning of September 1909, and in 
June 1924 and January 1925. It is evident that the pale aspect of the lake 
at times is also due to clouds, 

The five components of Solis Lacus which I noted in 1909, and which 
are shown in Plate III, are as follows: 

LUCIS portus. In 1894 Lowell drew a small dark spot at the NE 
extremity of the Solis Lacus. Douglass confirmed it in 1900-1. From 
Meudon, I have seen here a very strong dark patch, small, and indigo- 
greenish in colour. 

helii depressio. Dark and uneven core, observed in 1909 and 1924 
with the o m -83. It lies in the SE part of Solis Lacus. It was sombre in 
*9 2 4- 

vestte depressio. Dark, irregular patch of the Solis Lacus, lying to 
the N of Helii Depressio. 

FULGORIS depressio. Irregularly shaded, beautiful large patch; it is 
somewhat broken up. It lies in the SW part of Solis Lacus. 

phcebi depressio. Irregular dark condensation to the N of Fulgoris 
Depressio. It seems that in 1894 Lowell saw these four patches in geo- 
metrical form. 

ambrosia lacus. This is a small, broken-up lake, which I noted in 
1909 with the o m -83, toward the site of Ambrosia. I confirmed it, less 
strongly, in 191 1, 1924 and 1926. It was extended and very dark from 
Meudon in 1928-9. 

eosphori lacus. In 1 898-9 Cerulli drew a small dark patch on the 
Eosphoros; Lowell also saw it in 1907. From Meudon in 1909, it 
appeared very irregular (Fig 72); it was diffuse in 1911 (Fig 82) and in 
1924 (Fig 80). 



198 



phcenicis lacus (S, 1 877). Lying to the NW of Solis Lacus, this 
second lake is remarkable and very changeable. It is sometimes larger 
than our Lake Huron with its George Bay. It was observed as diffuse by 
Beer and Maxller in 1837 and 1839. Schiaparelli stated that Lassell had 
indicated it in 1862. Then, in 1877, Trouvelot drew it as making up part 
of the Phasis, which was then black; the Henry brothers, Dreyer and 
Green observed it as isolated. At this time Schiaparelli and the Henry 
brothers represented it as oblong, lying NE-SW, and almost as long as 
the Solis Lacus was broad. Subsequently Burton showed it in 1879, and 
Schiaparelli then saw it as smaller and triangular. To Bceddiekcr in 188 1- 
2 it was complex. It was again seen, though smaller, from Milan from 
1 88 1 to 1888, and in 1890 it was noted as double. Phcenicis Lacus 
appeared large to Hussey, Barnard, Campbell, Schscbcrle and Keeler in 
1892, and moreover Hussey showed it as broken to the S. In 1894 
Barnard, with Campbell, again showed it extended, Schseberle less so. In 
1909 1 was astonished to see it measuring at least 6", and appearing 
slightly indented to the S (Fig 85). Confused in 191 1, it seemed to me to 
be considerably diminished in 1924 (Fig 86); this was confirmed by 





3v 


* d 




• • 




1 


• 


^ 


IOOO 






Fig 85 (1909) and Fig 86 (1924) Change in appearance of Phrrnicis 
Lacus. (o m -8j refractor) 

Pease. In 1926 I saw it small and double, made up of two round lakes 

separated by an isthmus; the line joining the two was directed toward 
Solis Lacus. It was almost invisible with the o m -83 on 29 and 30 Decem- 
ber 1928 and 4 and 8 February 1929. 

In 1877 Schiaparelli found Phcenicis Lacus moderately dark; in 1879 
he saw it black. From Lick, it was often very sombre in 1892 and 1894. 



199 



In 1909, on 6 October, it struck the observer's attention; with the 
o'"'83 I saw it green indigo, almost black! Five days later it was very 
feeble. Phcenicis Lacus, Juventsc Fons, Ceti Lacus, Melas Lacus and the 
Agathodaimon to the E arc sometimes the darkest of all the patches 
visible on Mars with the great refractor. In 1894 Comas Sola believed 
that he had seen a reddish colour on Phoenicis Lacus with an o ni io8, but 
in fact this is impossible with so small an instrument. 

In 1909 the lake almost vanished below a mass of yellow cloud. It was 
consistently visible in 1924. 

columb/e tons. A small, strange lake, which I noted in 1924 closely N 
of Phoenicis Lacus {Fig 86). Can it be a part of the latter, separated by a 
cloud? This is not probable. 

LUX. In 1877, Green saw Phoenicis Lacus surrounded by a luminous 
aureole. From Mcudon in 1909, 1924 and 1926 I observed a whitish 
area touching Phcenicis Lacus to the N (Figs 85, 86 and 84). It some- 
times appears to whiten when seen obliquely. 

corvi lacus. In 1894 Stanley Williams noted a small lake to the ENE 
of Phoenicis Lacus — a marvellous observation with an o m i6 reflector. I 
confirmed this object from Meudon in 1909 (Fig 85). It seemed to me to 
be more extended, though feeble, in 1924 (Fig 83). 

iu-:n.\i.iA (S, 1877). This name was originally applied to the country 
bounded by the Araxes to the S, the Sirenius to the W and the Eume- 
nides to the NE, but to this I have added the country as far as the Hys- 
cus. Kaiser showed Daedalia lightly shaded in 1862, as did Trouvelot in 
1877 and Campbell, Stanley Williams and myself in 1894. From Meudon 
in 1924 it sometimes seemed less luminous than Thaumasia, and at this 
time Pease observed it unevenly shaded. I saw it as greyish rose. 

Daedalia sometimes whitens when seen obliquely, as SchiaparelH 
noted in 1879. 

on lacus. Observed by Lowell in 189410 the NVV of Phcenicis Lacus. 
On 2 September of that year Barnard saw it as large and black as the 
lake itself! Lowell and Dobbie drew it less extended in 1907, and so did 
I, from Meudon, in 1909 and 1911. 

arsia sylva (E, 1 894). This lake, lying to the WNW of Oti Lacus, was 



200 



seen double from Milan in 1890, and Keeler saw it as irregular in 1892. 
Campbell drew it small and sombre in 1894; Lowell also showed it. 
Eddie and Lowell again observed it in 1907. 

aganippe fons (L, 1 894). Another lake, to the S of Arsia Sylva, seen by 
Lowell between 1894 and 1897 and in 1907. 

gallinaria sylva (L, 1894). Yet another lake, to the S of Phcenicis 
Lacus, seen by Lowell at the same time as he detected Aganippe Fons. 

CANOPI FONS. Small lake situated in the SW part of the Araxes. I 
observed it from Mcudon in 1924. 

sirii fons. The most important condensation on the Araxes; it lies 
toward the centre. It was drawn by Lowell in 1896-7, by Eddie and 
Dobbie in 1907, by Graff in 1911 and noted by myself in 1924. 

canis fons. Another small lake on the Araxes, to the E of Sirii Fons, 
which I saw with the o m -83 in 1924. Pease, using the Mount Wilson 
2 m '57 reflector, also showed it. 

arcti fons. The fourth lake of the Araxes, to the SW of Phcenicis 
Lacus. I noted it from Meudon in 1924, and Pease confirmed it inde- 
pendently. 

p avon is lacus. Between Phcenicis Lacus and Ascraeus Lacus, Keeler 
in 1892 showed another lake. Lowell confirmed it from 1894 to 1897 and 
in 1907. I observed it extended in 1909, with the o m -83- 

tharsis (S, 1877). Bounded by the Tithonius Lacus and the Nox to the 
S, the Ulysses to the W, the Nilus to the N and the Chrysorrhoas to the 
E, this great stretch of desert land is shown lightly smoky on a drawing 
made in 1862 by Kaiser. Boeddicker found it dark orange; Keeler, red; 
Gale, reddish. I find it rose red, slightly greyish. 

On 18 and 19 January 1882, Schiaparelli saw Tharsis covered with 
white patches. 

Tharsis sometimes whitens when seen obliquely, as was shown on a 
drawing made by Lehardelay as early as 1871. 

On 13 January 1912, with the o m -83, 1 noted a yellow projection on the 
terminator here ; its height was 3 km. 

tractus albus. This is a great bright or whitish irregular streak, 



201 



extending from the Mare Acidalium as far as Lux, and measuring almost 
4000 km in length. It forms a Y with Candor. In 1879-80 Schiaparelli 
was struck by a beautiful whitish band joining Tcmpe to Phcenicis 
Lacus, crossing and weakening the double Nilus. This bizarre aspect 
was confirmed from Milan in 188 1-2; at the same time, Bceddicker also 
noted whiteness (Fig 87). In 1883-4 Schiaparelli again saw his streak, 




Fig 8y Whitish streak between the Mare Acidalium and Phamicis 
Lacus, observed by Boeddicker on 9 December 1881 (o m -gi reflector) 



but this time it was shorter and less luminous. In 1886 the Italian 
astronomer saw it as very bright, and parallel to the line Nilokeras- 
Chrysorrhoas. He saw it again, for the last time, in 1888. Later, in 
1898-9, Cerulli and Rheden saw it all along its length; Denning again 
drew it cutting the Nilus in 1903, and in 1907 Lowell and Lampland 
photographed the S part of it. Phillips and Thomson saw a white patch 
on Tharsis in 19 18, and Danjon clearly indicated the streak in 1920. On 
8 February 1929, with the great Meudon refractor, Tractus Albus was 
beautiful, forming the Y with the Candor. It is therefore a permanent 
feature which is often hidden by yellow clouds. 

ascr/eus LACUS (S, 1 888). Situated at the top of the Ceraunius, this 
other lake, twice as large as Lake Nyasa, is rather seldom well seen. With 
Mareotis Lacus it was rather uncertainly represented by Beer and 
Msedler from 1837 to 1841. Schiaparelli observed it extended in 1879; 
in 1881 -2, it saw it at least double; in 1883-4, clearly double; in 1886 
and 1888 large, black and single; in 1890, quadruple — as was also noted 



202 



by Lowell in 1900-1. In 1901 Attkins sometimes found it very sombre 
and conspicuous; W. J. Hall glimpsed it with a reflector of only o n, i2 
aperture. To Molesworth at this time it was dark, circular and diffuse. In 
1903 Molesworth found it reduced in size, Gale very pale; with my 
o n '-2i6 reflector I found it extended, diffuse and feeble. In 190^ Phillips 
found it large; in 1907, Buchanan saw it extended and feeble. From 



\ 



CI.' j 



Fig 88 Ascraus Lacus and Pavonis Lacus, 6 October /900. 
(o m -8j refractor) 

Meudon, it seemed of considerable size to me in 1909 and 191 1. Phillips 
noted it as excessively pale in 1913-4, as did Thomson in 1915-6. It was 
still large, but diffuse, to Brum It and Quenisset in 19 18 and to Danjon in 
1920. In 1924, with the o m '83, I could never see a trace of it! In 1926 it 
was very diffuse, and in February 1929 I saw it under poor conditions; 
it was then extended and vague. 

A lake such as Ascraus Lacus, surrounded by immense deserts where 
the wind whips up storms of dust, is more subject to obliteration and 
temporary extinction than a lake lying closer to seas. 

jovis lacus. Small dark patch, observed from Flagstaff to the SVV of 
Ascraeus Lacus between 1894 and 1895. This is Lowell's 'Lucus 
Jovis*. 

mareotis lacus. To the N" of Ascraeus Lacus, near the middle of the 
Ceraunius, there is an extensive variable lake, which Beer and Msdkr 
saw joined by a grey area to Ascraeus Lacus between 1837 and 1841. In 
1881-2, Schiaparelli recorded here several condensations on the double 
Ceraunius; in 1883 4 and 1890 he saw four nuclei where the Nilus 
intersected the double Ceraunius. Cerulli and Rheden, in 1898-9, drew 
some complex patches here. In 1 900-1 Attkins observed it, and noted 



203 



it as very evident in 1903, as did Phillips and Molesworth. In 1905 
Phillips found it extended and diffuse; in 1907, Eddie noted it very 
feeble. To me it appeared very diffuse in 1903, as it also did to Phillips 
in 19 1 5-6; and in 1920 Danjon showed it as more extensive than 
Ascrseus Lacus. In December 1928 I found it quite prominent. How- 
ever, it is not very often seen. 

Nix OLYMPIC* (S, 1879). This small white patch is situated near long. 
128", lat. h 21 , according to Schiaparelli, who described it as follows: 'I 
found it on 10 November (1879), and it was seen on the following nights 
up to the 17th; then, when the region again became observable, 1 saw it 
from 19 to 22 December. Altogether I made nine observations of it, in- 
cluding six determinations of position. It was as bright as the polar 




Fig 89 Nix Ofympica and whiteness on Arcadia, 11 November 1879, 
according to Schiaparelli. (o m -2l8 refractor) 

snow, but extremely small and very difficult to recognise, particularly 
during the December observations. On 10 No% r ember, between it and 
the canal of the Phlegethon, I seemed to see another white area, similar 
to that below the canal; on the next night I found that this appearance 
produced a sort of slender, oblique prolongation of one of the ramifica- 
tions of the polar snows, reaching almost as far as the Phlegethon and 
leaving a somewhat whitish patch as a boundary slightly beyond it. The 
whole system was arranged following a line which led directly to the 
Olympian Snow.'" Schiaparelli estimated that the diameter of the white 
patch was 4 , or a little more. 9 

Nix Olympica (Fig 89) was not again seen from Milan; however, on 
15 May 1888 a vague, extended whiteness was drawn in these latitudes. 









In 1903 Lowell drew a white patch here, confirmed by Briault in 1916 
and by G. Fournicr in 1920. 1 saw it well in 1926, with Lyot and Mile. 
Roumens; it measured some 8°, and appeared pale and uneven (Fig 90). 



\ ■■■ 



V 



Fig 90 Nix Ofympica, and neighbouring whiteness, on 1 November 192(3. 

(o m -83 refractor) 

With the o m -83 it seemed whiter on 29 and 30 December 1928. Then, on 
4 and 8 February 1929, it was invisible. It is undoubtedly a permanent 
topographical feature in the vast wildernesses of these regions. 

In 191 1 I saw it rise brilliantly on the terminator (Fig 91). It can also 
whiten when seen obliquely. 



e,M a 



Fig 91 Nix Ofympica, brilliant and sparkling at the periphery, on 
28 October 1911. (o m -83 refractor) 

Cyane FONS (L, 1894). Lake seen by Lowell in 1894 and 1896-7. In 
1898-9 Cerulli observed a small dark spot to the W of Ascraeus Lacus, 
which Fournier indicated on his 1920 planisphere. 

arcadia (S, 1881-2). Great desert region, in part smoky, contained 
between the Gigas to the S, the Pyri phlegethon to the SW, the Furotas 
and the Clarius to the N and the Ccraunius to the E. Kaiser drew it 
slightly shaded in 1864. This was confirmed by Niesten, Burton, 



204 



205 



Trouvelot and others, and by myself. It appears equally shaded-off on 
the photographs. Gale found Arcadia reddish; I have seen it red, but 
less smoky than Amazonis. 

These desert lands quite often whiten when seen obliquely. Trou- 
velot, in 1884, was the first to represent this phenomenon. 

alba. The NE part of Arcadia, between the Ceraunius and the 
Sirenus II, is whitish, and brighter than the rest of the land. In 1879 
Schiaparelli noted here the white streaks already described with Nix 
Olympica (Fig 89); from 1883 to 1886 he again distinguished these white 
features; in 1888, he noted a small white patch, about io° in diameter, at 
long. 120°, lat. +4°°; m '890 he once saw a whitish area in this position, 
corroborated during the same period by Stanley Williams. Attkins, in 
1 90 1, drew a large white patch here, elongated E-W; in 1903 Moles- 
worth observed something of the same kind, and Millochau drew three 
bright patches further to the S. To Ward, in 1905, the region was still 
luminous, and this was also noted by Phillips and Thomson in 19 17-8 
and G. Foumier in 1920. In 1926 I saw some whitish areas (Fig 90). 

ascuris lacus. Small lake, lying at the base of the Ceraunius; it was 
indicated by Schiaparelli in 1888 (Fig 144). Moles worth saw it again 
from 1900 to 1903, and G. Fournier and Danjon seem to have glimpsed 
it in 1920. 

tempe (S, 188 1-2), This continental region lies between the Nilokeras 
and the Kilus to the S, the Ceraunius to the W, the Tanai's to the N, and 
the Mare Acidalium to the E. It is bright, and according to Schiaparelli 
it is one of the lands of Mars 'which appears white most often.'™ Beer 
and Msedler generally saw it as pure red. 

It was observed as brilliant on the central meridian by Midler in 1841 ; 
Burton saw it luminous in this position in 1871, Trouvelot and Knobel in 
1873, Schiaparelli in 188 1-2 and 1888, Phillips in 1899, Quenisset in 
19 1 8, Mme. G.-C. Flammarion in 1920, 

Tempe often whitens when seen obliquely. This appearance, first 
shown on a sketch made by Herschel as early as 1781, was well repre- 
sented by Burton in 1879, and by Schiaparelli from 1 881 to 1890. From 
Milan, the region was sometimes seen to be as brilliant as the polar 






snows, and I noted whitish mists in 1896. Moreover, I saw it bright at 
sunrise once in 1900-1, and I observed it as radiant on the edge of the 
disk in 1903. Eddie in 1907, myself in 191 1, McEwen in 1913-4, 
Thomson and myself in 19 15-6 all saw it quite brilliant when near the 
limb on various occasions. 

On 5 and 6 July 1890, a visitor using the o" l -9i Lick refractor saw a 
point apparently detached from the terminator. Keeler recognised it as a 
projection hovering over Tempe. 

nix tanaica. Bright patch, sometimes brilliant, which is probably not 
due entirely to contrast; it lies to the W of the Mare Acidalium. It was 
noticed by Burton in 1871, and was subsequently observed by Green in 
1873, Lowell and Denning in 1903, Ward in 1905, Danjon in 1913-4, 
Thomson in 191 5-6, Quenisset and myself in 1918, and G. Fournier 
and Danjon in 1920. 

i.abeatis LACUS (L, 1894). In 1894 Lowell drew a lake in the middle of 
Tempe, confirmed by Molcsworth in 1896-7 and Cerulli in 1898-9. 
Attkins saw it oblong, Millochau shapeless, in 1 900-1. 

idjeus fons (S, 1890). In 1881-2, Schiaparelli saw a blackish point to 
the SW of the Mare Acidalium (Fig 104), which he reobserved in 1888 
(Fig 93) and in 1890. This lake was confirmed by Cerulli in 1898-9, 
Lowell and Molesworth in 1903, and Lowell again in 1905. It was also 
noted by Briault and Phillips in 1915-6 and by Phillips in 1918. 

lacus NiLiACUS (S, 1 879). This great sombre lake, to the S of the Mare 
Acidalium, is distinctly complex, and nearly always appears equal in size 
to our Lake Superior. It was drawn by Beer and Msedler as early as 1 830 
and 1837; Galle saw it in 1839, Maedler again in 1841, when to him it 
seemed filamentary toward the SW. Secchi in 1858 and Kaiser in 1864 
showed it diffuse, and joined on to the sea below. Nobody drew it in 
1862, as frequently happens at the time of oppositions which take place 
near perihelion. In 1871 and 1S73 Burton showed it as joined on to the 
Marc Acidalium. In 1873, Green showed it in the piquant form of an 
open hand, the fingers raised! Schiaparelli found it sharp and clear-cut 
to the N, patchy elsewhere; but he drew two bays to the S and the two 
estuaries of the Nilokeras to the W, which explains the description above 



206 



207 




Fig 92 Locus Niliacus and Mare Acidatium, 21 May 1918. 
(o m -32 reflector) 

as given by Green. I found it normal from Juvisy between 1896 and 
1 90 1 ; Molesworth noted it as small from 1896 to 1903. Thomson and 
Phillips drew it as rather restricted from 191 3 to 1916, 1 observed it well 
in 19 1 8, from La Frette, with the late Georges Barbier and using the 
o m -32 reflector belonging to his brother Andre. The lake was consider- 
ably extended and lenticular, lying almost along the parallel of latitude. 

The intensity of Niliacus Lacus is very great, particularly during the 
spring, though it is somewhat less than that of the Mare Acidalium. Very 
sombre to Msedler in 1841, it appeared blackish to Burton in 187 1, to 
Green and Burton in 1873, and to Schiaparelli and Terby in 1879. From 
1896 to 1909, from 19 1 3 to 1 9 18, and in 1929 I always noted it as less 
dark than the sea to the N. Millochau saw it patchy in 1903 ; G. Fournier 
recorded it as insignificant in 1920. Its colour appeared pale yellowish 
brown or sepia to Schiaparelli in 1881-2 (e = ±90°) and brown, though 
not really strong, in 1888 (e = 221°). 

Obliterated or yellowed from time to time by orange clouds, Lacus 
Niliacus can also have its northern part covered by whitish clouds. This 
was observed by Cerulli from 1894 to 1897, and by myself in 191 1, 1926 
and 1928. 



208 



endoris pons (L, 1903). This is the mouth of the Hydaspes on the 
Niliacus Lacus. It was seen by Schiaparelli from 1879 to 1882 as a dark 
spot (Fig 104) and was confirmed in 1903 by Millochau; it was also seen 
from 1903 to 1905 by Lowell, who called it 'Endor'. Briault showed it well 
in 1918, and G. Fournier drew it in 1920. 

engedii PONS (L, 1903). This is the estuary of the Jamuna on the 
Niliacus Lacus. Schiaparelli in 1879 described it as rather black, and 
saw it as a dark spot in 1 881-2. It was seen again by Millochau in 1903, 
and in 1903 and 1905 by Lowell, who named it 'Engeddi'. Briault in 
1918, and G. Fournier in 1920, drew it well. 

Jordan is pons. Dark nucleus, not well-marked, seen by Schiaparelli 
in 1888 at the NE extremity of Niliacus Lacus. 

achillis PONS (S, 188 1-2). More or less shaded isthmus, normally 
seen between the Niliacus Lacus and the Mare Acidalium. It is found on 
the sketches made between 1837 and 1841 by Madler, and Dawes drew 
it in 1864. Burton did not draw it either in 1871 or 1873, but in the latter 
year Knobel represented it as directed to the NW, an aspect which was 
not confirmed. Schiaparelli saw Achillis Pons in 1881-2; to him it 
seemed inclined toward the WSW from 1883 to 1888 (Fig 94). It was 
very shaded, often invisible in 1888 (Fig 95), and clear, parallel to the 
equator, in 1890. At this time Holden saw it as broad, and interrupted to 
the W by a greyish break. In 1898-9 Cerulli sometimes noted it as white. 
Quenisset saw it in 1918, when to me, in Andre Barbier's o m 32 reflector, 
it seemed greyish and inclined toward the WSW (Fig 92). I glimpsed it 
on 30 March 1929, on a disk only 7"o in diameter, with the Meudon 
refractor. From Milan it was seen as yellow in 188 1-2. 

mare boreum (S, 1 883-4). Name given to the totality of dark or 
patchy, shaded-off areas extending from Achillis Pons to the north pole 

of Mars. 

mare ACIDALIUM (S, 1881-2). This is much the most important of the 
dark areas of the Mare Boreum, and is more than twice the area of our 
Caspian Sea. It is bounded by the Achillis Pons to the S, by Tempe to 



209 



the W, by the shading of Baltia to the NW, and by Cydonia to the E, It 
was named Sinus Acidalius in 1883-4. Often, especially in the spring in 
the northern hemisphere, it appears as the darkest of all the seas. Its 
situation in the middle of continental areas means that its intensity is 
slightly exaggerated by contrast. It was first drawn by J. D. Cassini in 
1666, and Huyghens showed it in 1683. 11 Next, Hershchel represented 
it in 1779 and 1781 ; Schroter in 1792, Beer and Madlcr from 1837 to 
1841, Galle in 1839, Secchi in 1858, all saw it without difficulty. In 1871 
Burton, Gledhill and Terby showed it in the interesting form of a pear 
or balloon, 12 with the point at the bottom (Fig 93), and Burton again saw 




W§ 93 The Mare Acidalium, seen as pointed and blackish by Burton 
on 23 March i8yi. (O m -J05 refractor) 

this aspect in 1873; it then appeared very large, its breadth exceeding 
39 , which is exceptional. I was struck by this pear-shaped structure 
from Juvisy in 1 900-1, Schiaparelli had shown it in detail, as an irregular 
pentagon with the outer shadings of Baltia, Abalos and Nerigos below to 
the right (Fig 94). I confirmed this, notably in 191 8, together with G. 
Barbier (Fig 93), 

The great intensity of the Mare Acidalium has struck all observers. 
At an early stage, in the 17th century, Cassini and Huygcns represented 
it as very dark — more so than the equatorial and southern seas. Herschel, 
Schroter, Madlcr and Galle also drew it as sombre. It was pale in 1858, 
according to Secchi, and in 1867 according to G. Williams. On the very 
interesting sketches made by Burton in 1871, it appeared blackish. In 
1873 it was less intense, judging from the drawings made by Green and 
Burton. It was shown very dark by Boeddicker in 188 1-2, when Schia- 









parelli said that it was undoubtedly one of the blackest parts of the sur- 
face of Mars (Fig 104). In 1883-4 and 1886 (Fig 94) it was still very 




X « 



Fig <)4 Appearance of the Mare Acidaltum on JO March 1866, according 
to Schiaperalli. (o m -2i8 refractor) 

black as seen from Milan, and was the darkest of all the patches; but 
Schiaparelli referred to a lightening in 1888 (Fig 95), and in 1890 the 




Fig 05 Changes in the Mare Acidalium : 2j May 1888, according to 
Schiaparelli. (o m -4<) refractor) 

intense darkness seemed to him to be confined to the areas adjoining 
A chillis Pons, In 1896, on one evening with the o>"-24 at Juvisy, I saw 
an aspect which made me doubt the evidence of my eyes. In the lower 
part of the disk, above the polar mists, there was a patch as black as ink, 
and almost as intense as the darkness of the sky; it was the Mare Aci- 
dalium! (Fig 96). Later, in 1897, Phillips too was struck by the absolute 
blackness of this sea, and commented that it was with no doubt whatso- 
ever the darkest area that he had ever seen on the planet. In 1898-9 it 
seemed to me to be less sombre (Fig 97); in 1900-1 (Fig 98) and 1903 



210 



211 



(Fig 99) less still, and sometimes even slightly inferior to the Sinus 
Meridian!. In 1913-4, with the o m -2i6, it sometimes seemed darker 
than the Sinus Meridiani; in 1915-6 the two were about equal to me, 
though at this time Ellison again saw it as the darkest of all the areas on 
the planet. In May 191 8 I once more found it superior to the Sinus 
Meridiani. Ainslic noted it as less intense than in 1903. Then, in 1920, 
Quenisset and G. Fournier judged it dark; Mme. G.-C. Flammarion and 
Danjon drew it as less intense in 1920 and 1922. On 8 February 1929, 
with the great Mcudon refractor, I noted it as decidedly sombre when 
near the sunset border, and on 30 March it was darker. 





P*i 96 (2.5 November 1896), Fig 97 (24 February 1899), Fig 98 

(18 April 1901) and Fig 00 (31 March 1903) Progressive discolouration 

of the Mare Acidalium, during the Martian summer. (o m -240 refractor 

and o m -2l6 reflector) 

The tone here is not uniform. Schiaparelli drew numerous dark nuclei 
in 1888. Ten years later Ccrulli distinguished a medley of bright and 
shady areas, also seen by Molesworth in 1903 and Ward in 1905. The 
colour of Mare Acidalium is also variable. Thus, from 1871 to 1873 
Burton showed it as bluish-green (e = 181 and ± 210 ); from 1881 
to 1884 Rceddicker saw it as blue (c = 93° to 1 54°) ; in 1888 Schia- 
parelli recorded it as a not very striking brown (e = 221 ); in 1900-1 
Molesworth distinguished an indigo grey, with a blackish tint (e = 
160 ); in 1903 a greyish blue, with greenish tint (e <= 202 ); in 1913- 
4, Thomson gave a similar description (e = 105 ); in 19 18 and 1920 
I could glimpse only a clear grey, tinted with indigo (e = 204° to 
212 ); and Gale found it blue in 1920 (e = 210 ). Combining all these 
data, it seems that the Mare Acidalium comes out of winter as bluish, 
but dark to the point of being almost black, and becomes brown and 

212 







Fig 100 White clouds re-covering the Mare Acidalium : J November 1911. 

(o m -8j refractor) 



paler during summer and autumn (e = 220 ) after long exposure to the 
rays of the Sun. However, a large aperture is needed to distinguish the 
brown colouration. 

Mare Acidalium is often veiled by yellow mists. Under oblique light- 
ing it sometimes seems to be covered with white clouds which can hide 
it completely, as was represented by Kaiser in 1864, Lowell in 1903, and 
myself in 1909, 191 1 (Fig 100), 1926 and 1928-9. 

schema insula (S, 1881-2). Island, probably optical, glimpsed as 
Cimmeria Insula by Schiaparelli in 188 1-2, looking like a yellow star 
against the intense darkness of the Mare Acidalium (Fig 104). It was 
again drawn by Brown in 1896 and Briault in 1915-6. 

TUDERis pons. Sombre nucleus in the E part of the Mare Acidalium. 
It was observed by Douglass in 1898-9. Lowell confirmed it in 1905, 
calling it 'Tuder*. 

callirrhoes sinus. This is another very dark condensation in the 
Mare Acidalium, seen by Schiaparelli in 1888 at the mouth of the 
Callirrhoe, and confirmed by Molesworth in 1903 and Lowell from 1903 
to 1905. 

depressio acidalia. Very sombre nucleus in the middle of the Mare 
Acidalium, noted by Douglass in 1898-9. Molesworth recorded it in 
1903, and Lowell observed it from 1903 to 1905, calling it 'Lucus 
Acidalius'. 

acadinus fons (L, 1898-9). Another blackish spot, at the SW angle 
of the Mare Acidalium, noted by Douglass in 1898-9 and seen again by 
Lowell in 1903 and 1905. 

acidalius fons. Large, very sombre lake, on the Tanai's, to the N of 
Tempe. In 1888 Schiaparelli saw it only as a very dark broadening of the 
Tanai's. In 1896-7 and 1903 Molesworth saw an oval lake here. Lowell 

213 



observed it from 1903 to 1905, Briault in 1915-6; Danjon represented 
it as diffuse in 1920. 



IRREGULAR STREAKS AND MINOR DETAILS 

ACAMPSis (L, 1894). Horizontal band to the W of Solis Lacus, seen by 
Schaeberle, Lowell and myself in 1894. 

agathod;emon (S, 1 877). Blackish streak, convex to the SW, joining 
Aurora Sinus to Tithonius Lacus. In 1877 Schiaparelli recorded another 
branch going to the S, which I have called Nia. Beer and Maedler showed 
the Agathodaemon as straight in 1830. Secchi, Kaiser, Lassell, Lockyer, 
Knott and Rosse's observer drew it in 1862, Kaiser and Dawes in 1864. 
The Agathodajmon was extremely pale in 1877; the Henry brothers, 
Flammerion and Terby did not see it at all, but Harkness and Green 
drew it as feeble. Schiaparelli could only glimpse it. In 1879 it was not 
seen from Milan, though Niesten, Burton and Lohse represented it. 
From 1 881 to 1890 Schiaparelli drew it at each opposition. It was first 
seen as blackish by Holden in 1890; this was confirmed by Hussey, 
Campbell, Barnard and Schaeberle in 1892, and again by Barnard, 
Schaeberle, Campbell and Holden in 1894. In 1892 Hussey showed it as 
widened toward the N\V. In 1900-1 Millochau also indicated it as very 
dark and broadened to the right. Lowell photographed it in 1907 and 
1909. From Meudon, the Agathodaemon showed up admirably in 1909, 
convex toward the SSW, narrow to the E and broader to the NW, and 
blackish indigo, similar to the lakes to the right and to Juvcntae Fons 
(Fig 76). This aspect, confirmed by Graff in 191 1, seemed to me to be 
paler and more confused in 1924, but more vigorous in 1926 and 
1928-9. 

ambrosia (S, 1879). Band joining Solis Lacus to Coracis Portus. 
Schiaparelli drew it as broad in 1877 ( Fi g 81), and straight and always 
visible in 1879, when Niesten and Burton also represented it. In 188 1-2 
it was still well seen from Milan, but it was less marked in 1883-4, and 
was invisible in 1890. Schaeberle observed it in 1892, Campbell and 
Holden in 1894. With the o™-83 in 1909, 191 1 (Fig 82), 1924 (Fig 80) 
and 1926 (Fig 84) I could see it only as a small, isolated and broken-up 

214 






lake; but in 1924 I saw that to the right of the lake there was a dark band 
(Fig 80) bounding the greyness to the E. This was also seen by Pease. In 
1928, with the o m -83, I saw Ambrosia as well-developed. 

ARAXES (S, 1877). Very broad streak, cut-up and knotty, joining 
Phcenicis Lacus to the Mare Sirenum. The Araxes is shown on the 
drawings made by Secchi and Kaiser in 1862. Kaiser saw it again in 1864. 
There was enormous development here in 1877, when Trouvclot, the 
Henry brothers, and Lohse observed the Araxes as very much broad- 
ened, very sombre, and irregular (Fig 79). At this time Flammarion 
drew it as broad, particularly to the right (Fig 70); Schiaparelli showed 
it as narrow and sinuous (Fig 81). In 1879 Burton drew it, and the 
Italian observer showed it as less tortuous (Fig 71). In 188 1-2, from 
Milan, it was seen as a black thread; Boeddicker drew it broad and 
diffuse. Schiaparelli observed it again in 1888 and 1890. In 1892 Hussey, 
and in 1894 Campbell, Holden and Schaeberle indicated it as linear. 
From Meudon, in 1909, it appeared to be 6° broad, very irregular, and 
cut-up (Fig 72); in 191 1 it was billowy (Fig 82). In 1924, however, I 
found that it was extremely broad, irregular and knotty (Fig 80). In 1926 
I saw it broad, sinuous and diffuse (Fig 84). Schiaparelli saw the Araxes 
reddish in 1890 (e = 257 to 270 ); I saw it greenish grey in 1909 (e = 
8°). After 27 November 1924 I recorded it as chestnut vermilion, like a 
field of cornflowers (e = 30°). In 1929 it was pale vermilion (c = 1 1 1°). 

Bj<etis (L, 1894). This is a fine trail, sinuous and blackish, joining 
Gangis Sinus to Juventae Fons, and also bordering the shading to the 
left. It was vaguely shown on the coloured drawings made by Trouvclot 
and Green in 1877, and was suspected by Schiaparelli (Fig 81); but from 
1879 to 1890 Schiaparelli saw it as making up part of the Ganges. 
Hussey, Campbell, Barnard and Schaeberle drew the Baetis in 1892, 
pointing more to the NW than the Ganges; this was confirmed by Camp- 
bell in 1894. Millochau drew it as a sombre line in 1901. In 1909, with 
the o m -83, I saw it as a blackish thread, fine and undulating, making an 
angle of 160 with the Ganges, and bordering the shading of Xanthe 
(Fig 75). It was equally difficult later from Meudon. In 1924 Pease drew 
it as similarly narrow and irregular, using the Mount Wilson 2 m '57 
reflector. 



215 



bathys (L, 1894). Broad, irregular and knotty streak, of variable in- 
tensity, joining Solis Lacus to Aonius Sinus, and bordering the very 
light shading to the SE. In 1862 Kaiser saw it only as the boundary of the 
greyness above; in 1864 he drew the Bathys in its SW portion, and 
Dawes showed it feebly, as did Trouvelot in 1877. Burton saw it well in 
1879, Schiaparelli in 1890, Hussey and Schaebcrle in 1892, and Camp- 
bell, Barnard, Schsebefle, Holden and Stanley Williams in 1894. Lowell 
photographed it in 1907 and 1909 as the more intense edge of the grey- 
ness to the K. In 1909 I saw it excellently with the o m -83; it was broad, 
irregular, cut-up and knotty, bordering the half-tone to the SE (Fig. 72)! 
It was billowy from Meudon in r 9 i 1 (Fig 82), and extremely pale in 
1924, 1926 (Figs 83 and 84) and 1928. I noted it as green in 1009 (e — 
8° to 1 1°). 

calydqn (S, 1890). Line glimpsed by Schiaparelli near the site of the 
Tithonius. 

cantabras (L, 1894). Border of the shading to the N., joining Sinus 
Meridiani to Sinus Margaritifer in a curve concave to the S. Boeddicker 
observed it in this form in 1881-2. Rheden saw it as billowy in 1898-9. 
From 1900 to 1903 Molesworth saw it only as the border of the half- 
tone. This is also what I noted in 1924 (Fig 43), and it was confirmed at 
this time by Hubble's photograph. 

ceraunius (S, 1879). This is a large, ill-defined, vertical shading going 
from Lacus Ascreaius to Tanais-Clarius. Beer and Msedler represented 
it in confused form in 1837, as did Kaiser and Dawes in 1864, Burton in 
1 87 1, and others later. Schiaparelli also saw the Ceraunius in this form 
in 1879; but he saw it irregularly doubled from 188 1 to 1890, with 
branches which, according to the description he wrote to me, were 
'always broad' and more widely separated in the N. To me it appeared 
amorphous and smoky from 1896 to 1903 and in 191 1, as it also did to 
the Fournier brothers from 191 1 to 1914 and to Briault in 1918. Moles- 
worth found it easier when near the limb than when on the central 
meridian. Its colour was clear red as seen from Milan in 188 1-2 and 
1890, it was reddish to Quenisset in 1920, smoky vermilion and chestnut 
to me in 1928-9. 

chrysas (L, 1894). Line joining Juventaj Fons to Ceti Lacus. Hussey 
saw it in 1892. 



216 



chrysorrhoas (S, 1877). Knotty shading, convex to the WNW, 
broad to the S and narrowing to the NE, going from Tithonius Lacus in 
the direction of Luna; Lacus. Kaiser saw the Chrysorrhoas in 1864, and 
subsequently it was seen with certainty by Schiaparelli, Green and 
Lohse in 1873 and Niesten in 1879. f' rom Milan it appeared more or less 
rectilinear from 1877 to 1890, but double in 1883-4 ar *d l %9°> single in 
1886 and wavy at the edges in 1888. To me it seemed bent in 1896 (Fig 
96); this was also observed from Meudon in 1909, when it was very 
feeble, broad, diffuse and knotty to the S, but sharper toward Candor. I 
saw it less well in 191 1 and 1924. Schiaparelli found it reddish in 1888 
and 1890 (e = 220 and 274 ) and I found it chestnut in 1929 (e = 1 13 ). 

clarius (S, 1888). Broad streak, convex to the SSW, continuing the 
Tanais as far as Maeotis Pal us, and forming the boundary of the intense 
shading of Nerigos, It was indicated on the drawings made in 1864 by 
Kaiser. In general the Clarius was seen as sombre by Schiaparelli from 
1 88 1 to 1890, as the dark boundary of the half-tone to the NE. Boed- 
dicker also showed it in this form in 1883-4, and so did 1 in 1900-1. To 
Danjon it seemed dark in 1 920. 

dardanus (S, 188 1-2). Band seen between Niliacus Lacus and 
Mareotis Lacus. In 188 1-2 Bceddicker saw it only as the border of the 
shading to the S. Schiaparelli observed the Dardanus from 1 881 to 1884 
and in 1890, when to him it seemed somewhat irregular. To Millochau 
in 1 900-1, and to me in 1909, only formless shadings were visible here. 

EOSPHOROS (S, 1877). Narrow, irregular streak, going from Solis 
Lacus to Phcenicis Lacus. Kaiser saw traces of it in 1862. Trouvelot and 
Dreyer glimpsed only the NW part of it in 1877; but Green, Lohse and 
Schiaparelli drew the whole of it. Then, in 1879, it was seen from Milan 
as more difficult than it had been in 1877 ; it was also observed by Burton 
and Niesten. Evident in 1881-2, linear in 1883-4, lt appeared feeble to 
Schiaparelli in 1888 and 1890. Subsequently Hussey saw it in 1892, 
Campbell in 1894. From Meudon, in 1909 and 191 1, I saw it only as an 
isolated, very broken-up lake (Fig 72); however, in 1924 I saw it as a 
feeble greyish prolongation (Fig 80), and Pease saw it in similar form at 
the same time. It had the same appearance in 1926 (Fig 84). 

fortuna (S, 1879). Vague streak, going from Tithonius Lacus to 
Ascrasus Lacus. Observed by Burton and Schiaparelli in 1879, the 



217 



Fortuna was described as beautiful, darkish and narrow from Milan m 
1881-2. Schiaparelli saw it single from 1883 to 1886, double in 1888, 
single again in 1890. 1 saw it very ill-formed to the S and narrower to the 
N in 1909, from Mcudon; Danjon observed it as broad and pale in 1920. 
From Milan, in 1888, its colour was reddish. 

Ganges (S, 1877). This is a broad irregular streak, and the enhanced 
western limit of the shading of Xanthe. It extends from Juventse Fons to 
Luna: Lacus. As early as 1841, Maedler drew it as the border of this grey 
region. Next, Lasscll, Kaiser and Rosse's observer in 1862, and Kaiser 
in 1864, distinguished here an elongated shading. Dawes showed it as a 
straight, very fine line in 1865. Subsequently it appeared broad and 
diffuse in 1877, according to Trouvelot, Schiaparelli and Lohse. In 1879 
Niesten and Lohse drew it as the border of the half-tone; Schiaparelli 
showed it as a band. In 1 881-2, when Boeddicker could distinguish it 
only as the boundary of the shading of Xanthe, Schiaparelli showed the 
Ganges double. In 1883-4 Boeddicker repeated his observation given 
above; Schiaparelli saw the Ganges single, as he also did in 1886 and 
1888. In the latter year it had 'undulations on its two borders, which 
could be distinguished one from another'' 3 from Milan. In 1890 
Schiaparelli recorded it as double. In 1892 Hussey, Keeler and 




Fig 101 The Ganges and the liter, with the Lurier Lacus, jo September 
1924. (o m -83 refractor) 

Schaeberle saw it double, Campbell single, Barnard as the limit of the 
greyness (Fig 74). Schiaparelli described it as broad in 1894, Campbell 
almost double, Barnard always as nothing more than the edge of the 
shading. I glimpsed it as double for an eighth of a second from Juvisy in 
1899; Rheden distinguished it as the border of the half-tone. In 1909, 

218 



with the o m -83, 1 saw the Ganges as the broad, low-intensity boundary of 
the shading of Xanthe (Fig 75), and this is how it was photographed by 
de la Baume Pluvinel and Baldet. In 191 1, and from 1924 to 1929, 1 
confirmed the 1909 aspect (Fig 101), and so did Danjon in 1920. 
Quenisset saw it as very broad in 1922. Bidault de Fide found it intense 
in 1924, and Pease also represented it as very broad; this was confirmed 
by the photograph taken at the same time by Hubble, which showed it up 
principally as the border of the shading of Xanthe to the left. On 
3 September 191 1 Jarry-Dcsloges saw the Ganges made up of 'a great 
number of very small details . . . clear and quite well resolved; pale 
yellow, pale orange, greyish and fairly dark grey, separate from the 
clearer yellow ground". Burton believed that be had seen the Ganges 
bluish green in 1880 (e = 79 ); Schiaparelli found it reddish in 1888 
(e = 220 to 274 ); I saw it chestnut in 1912 (e = 87°), 1924 (e — 347 ), 
1926 (e = 6°) and 1929 (c ■■ 113 ), 

gehon 11 (S, 1888). Band going from Siloe Fons to the Mare Aci- 
dalium. Schiaparelli noted it from 1879 to 1888, and I believe I saw 
traces of it in 1 900-1. 

geryon (S, 1890). Line glimpsed by Schiaparelli between Sobs 
Lacus and Melas Lacus. 

halex (S, 1890). Line glimpsed from Milan between Ascraeus Lacus 
and Maeotis Palus. 

hydaspes (S, 1877). Very variable band, convex to the W, going from 
Margaritifer Sinus to the Lacus Niliacus. 'We know,' wrote Schiaparelli, 
'from the observations of Dawes and Secchi, that in 1864 and 1858 the 
Hydaspes was one of the most conspicuous of the canals, but this has not 
been the case during the period covered by my observations.' 14 There 
seems to have been a great change here, of a secular nature. According to 
Terby, the Hydaspes was seen by Maedler in 1841, and undoubtedly by 
Dawes in 1852. 15 However, it was first drawn clearly and described in 
detail by Secchi in 1858, when to him it appeared convex to the W, 
sombre, and narrower, if not actually interrupted, in the middle (Fig 
102). It was represented in part by Lials in i860 and by Lassell in 1862. 
Banks drew it with an o'"'095 in 1864, when Dawes showed it as straight 
and regular. Terby noted that Rosse probably observed the Hydaspes in 



219 




Fig 102 Secchi, 1858 (0^244 refractor) and Fig 103 Antoniadi, 1024 

(0 m -83 refractor) Extraordinary development of the Hydaspes in the 

middle of the 10th century 



1869, Lehardclay certainly in iSyi.' 6 On the other hand, while Burton 
also drew it in 1871 (Fig 93), Trouvelot did not see it in 1877, and 
Schiaparclli showed only the southern part of it. In 1879 Burton repre- 
sented it as convex to the W, broad and feeble; Schiaparclli made it 
rectilinear. To him, the Hydaspes was 'perfectly well observable, and, 
on 28 December, very broad and more evident than the Indus'. 1 ' In 
1 881-2 Boeddicker drew it as diffuse; Schiaparclli showed it convex to 
the W, and always indistinct (Fig 104). From 1883 to 1892 the Italian 
astronomer found it more or less pale. Schaeberle doubled it in 1892. In 
1896-7 Cerulli noted that it was easiest to see under oblique lighting. I 
sometimes suspected it in 1899, though it was very feeble indeed; it was 
even paler from 1901 to 1903, and in 1920 Danjon shaded in the part E 
of Chryse, beyond the Hydaspes. No trace remained of it in 1924 (Fig 
103) or 1926. Secchi saw the Hydaspes pale blue in 1858 (e = 263 ), 
Schiaparclli reddish in 1888 (e = 236°). 

Thus this strange streak appeared very much in evidence in 1852, 1858 
and i860, almost disappeared in 1862, and again became easy to see in 
1864, 1869 and 1 87 1. It was very pale in 1877 and lightly reinforced in 
1879 and 1899, after which it became excessively pale or even invisible. 

220 



hydbaotes (S, 1881-2). Edge of an indefinite penumbra, impercep- 
tible toward the NE, and sometimes glimpsed as a line connecting the 
Margaritifer Sinus to the Lunae Lacus. Schiaparelli noted it partially 
double in 188 1-2 (Fig 104), single to the SE and double to the NW in 
1883-4, double in 1886, and single in 1888 and 1890. Schaeberle showed 
it in 1892. My drawings made in 1909 show it only as the border of a 
very feeble shading toward the NE, but in 191 1, from Meudon, I saw it 
as a broad band on Xanthe. Pease's drawing and Hubble's photographs 
show no trace of it in 1924, though these observations were made with 
the most powerful instrument in the world. Schiaparelli found the 
Hydaspes brick- red in 1886. 

HYSCUS (L, 1894). Wavy streak, sometimes appearing as the darkened 
border of Icaria to the SW. It extends from Aonius Sinus to Sirenum 
Sinus. As the boundary of the greyness, it is suspected on Schroter's 
sketches of 1800 and on those made by Beer and Madler in 1836. In 1862 
Lockyer showed only a streak in this position, the shading beginning a 
little further toward the SW; but Secchi, Banks, J. Phillips and Rosse's 
observer all showed the Hyscus as the strengthened border of the half- 
tone. At this time Lassell drew it as a vigorous band. In 1892 Keeler, 
Hussey, Schaeberle and I saw the same aspect (Fig 108), but the boundary 
was then concave toward the NE ; Campbell drew the Hyscus only as a 
broad, irregular streak. In 1894 Barnard, Campbell and Schaeberle still 
observed the edge of Icaria as concave. This was confirmed by Crouzel 
in 1907. In 1909 and 191 1, from Meudon, the Hyscus appeared as the 
boundary of the strong greyness to the SW, but the section leaving the 
tip of Sirenum Sinus was slightly concave to the NE, as was fully con- 
firmed by Lowell's photographs. In 1924 1 noted the Hyscus as irregular 
and decidedly thin; I was using the o m -83 (Fig. 80). The greyness of 
Icaria began well beyond, toward the SW, at about 400 km. from the 
extremity of Sirenum Sinus.* It was feeble in 1926. 

[NDUS (S, 1877). Irregular streak, knotty and changeable, joining the 
Margaritifer Sinus to the Lacus Niliacus in a curve convex to the E. To 
the N, it limits the shading of Oxia. The Indus was drawn as blackish by 



* See below: [curia and Herculia Columns:. 




221 



Herschel in 1783. Galle, and Beer and Msedler in 1839, and Midler in 
1841, drew the Indus as very beautiful; very broad and very intense. It 
was then highly developed. Secchi did not see it in 1858, and nobody 
drew it in 1862. Dawes sketched only the S part of it in 1864, but at this 
time Kaiser did not see it at all. In 1873 Burton noted it as strongly 
curved, but feeble. Green drew it in 1877; Schiaparelli did not dis- 
tinguish it until 1878— on a 5*7 disk! In 1879 Niesten showed it as the 
border of the shading to the NE, and Burton showed it clearly. At 
around this time Schiaparelli always found it easy, broad and very dark. 
In 1 88 1-3 the Indus appeared to him as 'the most distinct and most easily 
visible of all the canals', 18 it was broad, obvious and sombre, with its 
curvature greater in the middle than at the ends, so that it resembled an 
hyperbola (Fig. 104). At this time Bceddickcr also drew it as broad and 
intense. In 1883-4 lt wa s much in evidence to both these observers, but 
from Milan in 1886 it was not so prominent. In 1888 it was even less 
conspicuous, but by 1890 it had again become broad and dark. In 1892 
Barnard showed it sombre to the S. To me, it never appeared really 







Fig 104 The Indus, seen in developed farm in 1882, according to 
Schiaparelli. (o m -2i8 refractor) 

dark from 1894 to 1903 (Figs 97 to 99), In 1903, with the o'u-83, 
Millochau showed it knotty and convex to the E, an aspect confirmed by 
Eddie in 1907. From Meudon, in 1909, I also saw it as curved back and 
hyperbolic (Fig. 56); it was similar in 1911, 1934, and 1926 under poor 
conditions. It was broad and intense in March 1929. Hubble's photo- 
graph of 1924 showed it convex to the NE, and broadening the shading 
of Oxia. Burton saw the Indus bluish green when it was intense in 1880 

222 






(e = 79 ); I saw it chestnut in 1929 (e = 135°)- 

iris (S, 1879). Vague knotty streak, joining Phcenicis Lacus to 
Ascraeus Lacus. It was observed by Niesten in 1879, and by Schiaparelli 
from 1879 to 1890. From Milan in 1879 the Iris appeared very narrow 
to the S, as a very thin penstroke ; in 1883-4, tnc Italian astronomer drew 
it double. Schaebcrle showed it in 1894, and from Meudon in 1909 it was 
very feeble and smoky. Schiaparelli found the Iris clear red in 1881-2 
and 1888. 

issedon (S, 1 88 1 -2). Narrow, difficult band, observed from Milan 
between the Lunae Lacus and the Tanais from 1881 to 1884 and in 1890. 

ister. Fifteen degrees to the E. of the Ganges there is a broad, irregu- 
lar streak, virtually parallel to the Ganges, to which I have given the 
name of Istcr. Keelcr represented it accurately in 1892; Rheden saw it in 
1898-O. Lowell and Lampland photographed it in 1907, de la Baume 
Pluvinel and Baldet in 1909; Danjon drew it in 1920. With Baldet, at 
Meudon in 1924, I saw it as large, of irregular breadth, uneven, and 
chestnut-colour (e = 347 ) (Fig 101). I saw it similarly in 1926. 

jamuna (S, 1879). Border of the shading of Xanthe, to the E, going 
from Tamunse Sinus to the Niliacus Lacus. The Jamuna is feebly shown 
on the sketches made by Beer and Maedler from 1839 to 1841, and also 
on those of von Franzenau in 1864; at this time Kaiser, with his custo- 
mary precision, recognised it as the boundary of the greyness to the W. 
Dawes saw it to the N, linear and very narrow. 19 Niesten, in 1879, again 
showed it as the border of the half-tone. At this time Schiaparelli 
glimpsed the Jamuna as being convex to the WNW and broad, especially 
to the left. In 1882 Bceddicker showed it only as the border of the shad- 
ing, but Schiaparelli made the Jamuna double (Fig 104) — though he 
subsequently saw it as single until 1892. From Milan, in 1890, he 
measured its breadth as 17 km! At this time Holden drew it as a diffuse 
band, as did Schiaparelli in 1892. With the Juvisy o m -24, I glimpsed it 
as double for an eighth of a second in 1894, and at the same period this 
was confirmed by Cammell. Later, it appeared to me as diffuse and pale 
(Figs 97 and 98). From Meudon, I saw it in 1909, 191 1, 1924 and 1926 
only as the broken-up border of Xanthe (Fig 101). Schiaparelli saw the 
Jamuna reddish in 1888. 




223 



jORDAN-rs (S, 1881-2). Name given to a line glimpsed from Milan in 
188 1-2, between Ismenius Lacus and the Mare Acidalium. In 1883-4 
and j 886 it appeared to join Dirce Fons to the preceding sea; but in 1.890 
Ismenius Lacus was double, and coming out of it Schiaparelli saw two 
parallel straight lines, called by him the Jordanis, of which the S branch 
went to the Lacus Niliacus. To avoid confusion with the neighbouring 
band of Gehon II, I have given the name Jordanis to the streak which, as 
a continuation of the Dcuteronilus, goes from Dirce Fons to Lacus 
Niliacus. Holden, among others, drew the Jordanis broad in 1888, and 
it was diffuse to Danjon in 1920. 

nectar (S, 1879). Beautiful irregular streak, broad, cut-up and knotty, 
going from Aurora: Sinus to the Solis Lacus, and limiting the greyness of 
Thaumasia to the S. It was the 'tail of the pear' of Solis Lacus, and its 
principal outlet. The Nectar was drawn by Beer and Midler as early as 
1830, and was well represented in 1862 by Lassell, Rosse's observer, 
Lockyer and Kaiser; it was drawn as very straight by Kaiser and Dawes' 
in 1864. In 1877 two feeble parallel streaks were traced here by Trouvelot 
(Fig 79); Dreycr and van Ertborn at this time showed the Nectar as 
excessively pale. The fact that neither Flammarion (Fig 70), the Henry 
brother* Niesten, Terby, Lohse, Harkness nor Schiaparelli (Fig 81) 
drew it in 1877 shows that in that year it must have been extremely pale, 
and Solis Lacus had lost its left extension. Subsequently, the Nectar was 
shown by Burton and Schiaparelli in 1879 (Fig 111 then by Breddicker 
and Schiaparelli in 1 881-2, when it was sombre. From Milan it was again 
seen from 1883 to 1890, except in 1886. Holden showed it well in 1890. 
It was again shown as broad and dark on the drawings made by Hussey 
and Campbell in 1892, feeble on those of Schseberle; it was invisible to 
Barnard on 19 August. Subsequently, it was extremely broad to Holden 
and Campbell in 1894. It was first photographed by Lowell and Lamp- 
land in 1907; on these photographs it was shown as extending up to the 
boundary of the greyness to the S. With the o"'^, in rgog, I saw it as 
intense, broad and broken-up, with undulating borders and a knotty 
structure under the upper penumbra. It was also very broad in I9 ii-2 
to Danjon and myself (Fig,8a). Bidault dc lisle still showed it broad in 
1924; at this time it again very broad, irregular and decidedly dark (Fig 

224 






8o), an aspect which was confirmed by Bubble's photograph. The aspect 
in 1926 was the same (Fig 84), but on 29 and 30 December 1928 it was 
almost invisible with the o'"^; then, on 9 February 1929, it was seen as 
directed toward the ENE. 

Schiaparelli saw the Nectar directed ESE from 1879 to 1886; in 1890, 
toward the ENE, when he named it Tyndaros. I observed it as clearly 
greenish in 1909, with the o'"-83 (e = 8° to n°). 

nia. Narrow streak joining Ceti Lacus to Nectaris Fons. Schiaparelli 
observed it from 1877 to 1884 and in 1890, Hussey in 1892. To me it 
appeared as clear, fine, feeble and wavy in 1909, and I glimpsed it as a 
thread in 191 1 and 1924 (Figs 78 and 80). 

nilokeras (S, 1881-2). This is a very remarkable streak, broad and 
intense, limiting the shading of Xanthc to the N, and made up princi- 
pally of two large irregular bands, of which the lower is the stronger. 
These bands separate toward the NE, and join Luna; Lacus to the Lacus 
Niliacus and to the Mare Acidalium. The Nilokeras was drawn broad 
and dark in 1839 and 1841 by Beer and Maedler. Jacob saw it in 1854; 
and in i860 Liais represented it as intense and broadened toward the NE. 
Dawes observed it irregularly double in 1864, but Kaiser saw it only as 
the border of the Xanthc shading. Burton showed it very extended and 
convex to the SE in 1871 (Fig 93) and 1873, which is correct; it was also 
confirmed by Green in the latter year, while Terby glimpsed it with an 
o"«io8 telescope! In 1877 Trouvelot showed it as diffuse and broad, 
particularly to the left. Confused to Schiaparelli in 1877, it appeared 
linear to him in 1879, and irregularly double in 1881-2 (Fig 104); in this 
year Bceddicker distinguished it only as the border of the shading to the 
S. Subsequently it appeared single, but indented, from Milan in 1883-4. 
Using an o">-i6 refractor at Meudon, Trouvelot then saw it as very 
intense. It was again single to Schiaparelli in r886, but once more 
double in 1888 (Fig 95) and 1890— the N branch going to the Mare 
Acidalium and not to the Lacus Niliacus, as in 1881-2. This aspect was 
confirmed in 1890 by Holden, who showed the N component as much 
more sombre than the other, as had already been noted in 1888 and 1890 
by Schiaparelli. I saw the Nilokeras generally dark, sometimes diffuse, 
from 1894 to 1903 (Figs 96 to 99), and Lowell and Lampland photo- 



225 



graphed it in 1905. In 191 1-2, from Meudon, I noted it simply as the 
border of the shading of Xanthe. Then, in 1918, it seemed to me intense 
and broad, particularly to the XE. In 1920 Danjon drew it as very 
extended, and double, with the lower branch flowing into the Mare 
Acidaliurn. In March 1929, with the C'-Sj, I saw it as broad and sombre. 
In 1890 Schiaparelli was surprised to see the bands of the Xilokeras 
intense red in colour; the redness was very vivid, and he called it "streaks 
of blood' (e = 274 ). 

NILUS (S, 1881-2). This name was originally given to the long streak 
which emerged from the X point of the Syrtis and went as far as 
Ceraunius; but in 188 1 -2 the band was divided, from the E to the W, into 
five segments: the Nilosyrtis, the Protonilus, the Deuteronilus, the 
Xilokeras and the Xilus. The latter thus joins the Lunae Lacus to the 
Ceraunius. It is a broad band, smoky and indefinite. M&'dlcr drew the 
Nitusinthisfonnin 1841. Burton in 1871, and Tcrbyand Lohse in 1873, 
agreed with Manlier in this respect. It was still diffuse to Schiaparelli in 
1877 and Burton and Xiesten in 1879, when it appeared double from 
Milan and continued to do so up to 1890. Ba-d dicker in 1 88 1-2, Terby in 
1888 and I in 1896-7 observed it as broad and smoky; but in 1899 I 
once glimpsed it double with the Ganges for an eighth of a second. 
Lowell and Lampland photographed it in 1907; Danjon noted it as 
broad and billowy in 1920. Schiaparelli saw the Xilus brick-red in 1886, 
and red in 1888 ; in the latter year this was confirmed by Terby (e = 221° 
to 224 ). 

NOX. W part of the Agathodatmon ; broad, and strikingly less dark than 
the rest. It was clearly defined on Mtedlcr's planisphere of 1838. It was 
drawn by, among many others, Secchi, Lockyer, Rosse's observer, 
Lassell and Kaiser in 1862; Dawes and Kaiser in 1864; the Henry 
brothers and Xiesten in 1877; Schiaparelli from 1877 to 1890; Xiesten 
and Burton in 1879; Guillaume in 1890. With the o'"'83, in 1909, I saw- 
it broad and pale (Fig. 76). It was the same in 1911, and in 1924 it was 
still broader (Fig 80), of striking chestnut-red colour (e = 30 ). I again 
saw this hue clearly in 1929 (e = 113 ). 

oxus 1 (S, 1879). Knotty streak, convex to the XW. It is intense, and 
goes from Oxia Palus to Siloc Fons, bordering the half-tone of Oxia. It 



226 



was shown on a drawing made by Kunowsky as early as 1841. The Oxus 
I was very broad and prominent to Maedler in 1841. Secchi in 1858 and 
Green in 1877 showed here an enhanced boundary toward the shading 
to the N W. Holden saw the Oxus I as broad and very sombre in 1 879 ; 
Schiaparelli showed it as linear in 188 1-2 (Fig 104), while Burton and 
Bceddicker represented it as very feeble. From Milan in 1883-4 it 
appeared broad and intense between the Gehon I and the Deuteronilus, 
and it was still evident from 1886 to 1892. Millochau drew it diffuse in 
1903, when with my o ni -2i6 reflector I saw it as very knotty. Rudaux 
saw it in 1905 with an o m 095 telescope. Pale in 1909 and 1911, from 
Meudon, it was intense to Bnault in 19 18, and in 1924 it seemed to me to 
be easy, extended toward the left. Using Ritchey's 2 m '57 reflector, Pease 
drew it as bordering the shading of Oxia. 

For the sake of clarity, I have divided the Oxus into two parts. 

phasis (S, 1877), Streak, variable in intensity, going in a curve convex 
to the W from the Aonius Sinus to the Phcenicis Lacus. According to 
Schiaparelli, the Phasis was indicated by Kaiser in 1862, when Secchi, 
Lassell and Rosse's observer drew it as sombre and concentric with Sol is 
Lacus. It was the scene of exceptional development in 1877, when the 
Phasis, with the Aonius Sinus, became extremely sombre or even black- 
ish — and striking as seen in an o m -io8 telescope! The contemporary 





Fig 105 Trouvelot, 1877 (o m -j8 refractor} and Fig 106 Antoniadi, 

1924 (o m -8j refractor) Exceptional development of the Phasis and 

Aonius Sinus in 1877 

drawings by the Henry brothers, Flammarion (Fig 70), Trouvelot (Fig 
I0 5). Green, Terby and Schiaparelli (Fig 81) are in full agreement on 



227 



this point. From Milan, the Phasis was then regarded as easier than the 
Agathodsemon, with 'a very complex estuary in the form of a water- 
spout*. 30 This aspect had become even more striking in 1879, when 
Schiaparclli described the two bands of the Phasis as 'assuredly one of 
the most beautiful canals which exists on Mars' 21 (Fig, 71), Burton also 
saw it well. Schiaparclli found it feeble in 188 1-2 and 1888, more intense 
in 1890. Hussey, Campbell, Barnard and Schaeberle again drew it in 
1892; Campbell, Schscberlc and Barnard in 1894. Then, in 1924 and 
1926, I found from Meudon that the Phasis was convex toward the \V; 
it was of uneven breadth, extremely smoky and feeble, and sometimes 
marking the limit of the penumbra of Daedalia (Fig 80). Schiaparclli saw 
the Phasis bluish-grey at the time of the great development of 1877 
(e = ±50°), reddish in 1890 (c = 252°). 

SIRUS (S, 1888). Line glimpsed from Milan in 1888 and 1890, between 
Siloe Fons and the Mare Acidalium. 

Tanais (S 1881-2), Broad streak, knotty and sombre, emerging 
from the NW of the Mare Acidalium and forming the S boundary of the 
very strong shading of Baltia. 'Its importance,' wrote Schiaparclli, 
'ought not to be regarded as less than that of the Mare Chronium.* 22 The 
Tanais was drawn as early as 1792, by Schrceter. Beer and Msedler in 
1837, Secchi in 1858, and Trouvelot, Green, Terby and Lohse in 1873 
saw it only as the border of the half-tone of Baltia. This was confirmed 
by Bceddicker in 1881-2, when to Schiaparclli the Tanais seemed very 
black. From Milan, from 1883 to 1890, it was always seen as broad and 
dark, bordering the greyness of Baltia (Figs 94 and 95). In 1883-4 '* was 
classed as a strait rather than as a canal; and in 1888 it appeared parti- 
cularly blackish to the E as far as Acidalius Fons (Fig 95). Holden also 
observed it as very broad in 1890. Between 1900 and 1903, I distin- 
guished it as the boundary of the shading to the N (Figs 98 and 99), as 
did Danjon in 191 3 and 1920 and Qucnisset in 1918. 

The white streak coming from the northern polar snow to the Lacus 
Pheenicis, seen in 188 1-2, was described by Schiaparclli as making the 
Tanais become narrower near lat. 60 1 . 

TITHONius (L, 1894). This is a broad streak, continuous and undulat- 
ing. It is of variable intensity, and joins Solis Lacus to the Tithonius 



228 



Lacus. Trouvelot sketched it in the form of vague streaks in 1877. It 
was drawn as reasonably broad and diffuse by Bceddicker in 1881-2, 
Wislencius in 1890, Hussey, Barnard, Campbell and Schseberle in 1892, 
Barnard and Campbell in 1894. Lowell photographed the Tithonius 
clearly in 1909, when, using the o n, -83, I found it very easy; it was 
broad, with wavy borders, continuous and slightly knotty. In 191 1-2 it 
was much less conspicuous (Fig 82). Danjon did not see it in 1920. In 
1924 Bidault de I'Isle drew it, and I noted it as sinuous and extremely 
feeble (Fig 80) ; but in 1926 and 1928-9 I found it very sombre and broad, 
invaded by Solis Lacus (Fig 84). I made it greenish in 1909 (e = 8° to 
1 1°), and it was green in 1926 (e - 20 to 44 ), brown in 1928 (e = 93 ), 
grey in 1929 (e = 113 ). 

tyndaros. See Nectar. 

ULYSSES (L, 1894). Vague streak and grouping of disconnected spots 
between Sirenum Sinus and Ascra;us Lacus. In 1879 Schiaparclli saw a 
confused shading here, and he made it double in 1890. In 1892 Campbell 
and Keeter drew it as a vague band ; Barnard saw it better toward the N'E 
in 1894, and in 1920 Danjon saw it as broadened and diffuse. 

Ura.nius (S, 1 881-2). Feeble diffuse streak, going from Lunie Lacus to 
Ascrams Lacus. Trouvelot in 1877, Burton in 1879, and Bceddicker in 
1881-2 showed traces of it. In the latter year Schiaparclli found the 
Uranius easy and diffuse; it seemed to him to be double in 1883-4, single 
in 1886, invisible in 1888, double in 1890. In the latter year Holden saw 
it as broad, but single. In 1920 Danjon could see it only with difficulty. 
From Milan, the Uranius was seen as of a curious red colour in 1883 4. 

References 

1. FLAMMARION, La planete Mars. vol. I. p. 440. 
z. Memoria II, p. 47. 

3. FLAMMARION, La planete Mare. vol. I, p. 475. 
4- Ibid., p. 146. SECCHI, op. cit., 1863. 

5. Seven months after the publication of this original observation (Bull, de la Soc 
Astr. France, vol. 40, 1926, pp. 4 oy and 512-3, fig Z16-7), W. H. Pickering again 
announced the change in the lake, without mentioning the Meudon results (['<ii> 
Astr. vol. XXXV, 1937, p. 199). 

6. Memoria III, p, 30. 
7- Memoria I, p. 35. 
•*. Memoria II, p. 75, 



229 



9. r'LAMMARION, La planet c Mars, vol. I, p. 441. 

10. Memoria III, p. 26. 

it. Announced by TERBY (Arcofjraphie. pp. u and oH). 

12. r'LAMMARION, La planetc Mars, vol. I, p. 209. 

13. FLAMMARION, La planetc Mars, vol. I, p. 422. 

14. Ibid, vol. I, p. 447. 

15. Arcographie, p. 72. 

16. Ibid, pp. 72-3. 

17. Memoria II, p. 56. 

j 8. Memoria III, pp. 21-2. 

10. This was noted by Burton (Trans. Roy. Dublin Soc. 

20. Memoria 1, p. 58. 

21. Memoria II, p. 64. 

22. Memoria III, p. 25. 



[SSo, p. 172.) 



Mare Sirenum and Mare Cimmerium 



palinuri SINUS, This important gulf, lying to the E of Palinuri Fre- 
turn, was seen by Beer and Maedler as early as 1830. Kaiser in 1862 and 
1864, and Trouvelot in 1877, showed it as sombre. To me, from Juvisy, 
it appeared very pale between 1894 and 1897, but from Meudon in 1909, 
191 1, 1924 and 1926 I saw it as a strongly shaded patch. The colour of 
Palinuri Sinus was pure green in 1909, as seen with the o" 1 ^ {e m 8°); 
brown in 1924 (after e = 32 1°); and in 1926 green at first (e = 337°) 
and then brown (e = 21 to 60°). 



palinuri fretum (S, 1877). L ying between Thyle I and Phsethontis, 
this sea-arm was shown by Beer and Msedler in 1830, Schmidt in 1845, 
Loekyer and Rosse's observer in 1862, Kaiser and Dawes in 1864, and 
the Henry brothers, Terby, Green, Dreyer and Schiaparelli in 1877. All 
these observers saw it reasonably well. In 1909 I found it narrow, 
irregular and patchy as seen from Meudon ( Fig 139). In 1924, after 
9 August (e = 321°) the channel was chestnut-brown as seen with the 
o n '-83, and this was also the case in 1926 (e = 14 to 6o°). 

FAM/E DEPRESSio. Small dark patch in the most cut-up part of Palinuri 
Fretum, I saw it from Meudon in 1924. 

mare chronium (S, 1 877). This is an inland sea of considerable 
importance, though it is not very dark. It lies between the Thyle islands 
to the SE and the SW, and Electro and Eridania to the N. It is open to 
the E and to the W to the arms of Palinuri Fretum and Tiphys Fretum, 
and to the S on Ulyxis Fretum, It therefore presents some sort of analogy 



230 



231 



to the Sea of Marmara and its channels to the Bosphoros and the 
Dardanelles. It was first shown in 1704 by Maraldi, and then, in 1783, 
by Herschel. Beer and Msedlcr saw it well in 1830 with their o'"-ioo, 
telescope, but to them it was less clear in 1832. Schmidt in 1845, Kaiser 
and Dawes in 1864, and Flammarion, Terby, Nicsten, Harkness, Green 
and Schiaparclli in 1877 all drew it satisfactorily. Keelcr saw it narrow 
in 1892, and using the o m -83 I saw that its coasts were irregular (Fig 

139)- 

Maraldi, Schiaparelli and many others have described it as less dark 

than Mare Sirenum, and this is in accord with my own observations. 
However, the Milan astronomer found the Mare Chronium very black 
in 188 1-2, To me it seemed decidedly feeble in 1894, normal in 1909, and 
patchy in 1924 as seen from Meudon (Fig 107). In 1909 it seemed to 
me to be greenish indigo-grey (e = 2 to 29°); in 1929, chestnut-brown 
after 9 August (c = 322 ); in 1926, chestnut (e = 14 to 6o°). 

SIMOENTIS SINUS. This is the mouth of the Simois on to the Mare 
Chronium. Schiaparelli represented it from 1877 to 1882, and in 1909, 
from Meudon, I saw it broadened to the S in a vast greenish-grey trum- 
pet form (Fig 133). On a small scale the Simocntis Sinus, together with 
Dryad is Palus and the Simois, recalls the aspect of the Syrtis Major with 
Maeris Lacus and the Nilosyrtis. 

ach/eorum portus. Estuary of the Scamander on the Mare Chronium, 
drawn by Schiaparelli from 1877 to 1882. With the o ni -83 1 see it as 
moderately pointed. 

XANTHI SINUS. Mouth of the Xanthus on to the Mare Chronium, also 
shown from Milan from 1877 to '882. To me, from Meudon, it seems 
much less important than the mouth of the Simois. 

danaidum depressio. Sombre patch in the Mare Chronium, to the 







Fig loy Knotty aspect in the Mare Chronium, 12 October 11)24. 
(o m -83 refractor) 



232 



XW of Thylc I. I observed it in 1924 (Fig 107). 

meropes depressio. Another dark patch in the Marc Chronium, to the 
S of Eridania (Fig 107), seen by me in 1924. 

nepheles depressio. Yet another sombre patch in these latitudes — 
this time on Tiphys Fretum. I observed it in 1924 (Fig. 107). 

tiphys fretum (S, 1877). Channel, forming a connection between the 
Mare Chronium, to the \V, and Promethei Sinus. Beer and Mzedler 
showed it in 1830, Schmidt in 1845, Lockyer in 1862 and Kaiser in 1864. 
The Henry brothers, Terby, Schiaparelli and Green also drew it in 1877. 
Many other observers have seen it since. With the o m -83, I found it 
irregular in 1909 (Fig 139), when it was darker than Palinuri Fretum; at 
this time Hale photographed it as darker than Promethei Sinus. I found 
it pale in 191 1, patchy in 1924; in this year it turned chestnut-brown 
(e = 338 ). It was also chestnut in 1926 (e = 14 to 6o q ). 

icaria (S, 1877). Originally this name indicated the partly very shaded 
land extending between the Aonius Sinus, the Herculis Columnar, the 
Mare Sirenum and the A raxes. On my map it goes only as far as 
the Hyscus. The S coast diverges here from the Mare Sirenum. Icaria is the 
first of a chain of smoky lands aligned on the 45th parallel as far as Hellas, 
extending over 9000 km in length. The shadiness of the region was noted 
by Herschel in 1783, and Schrocter also saw it in 1800. It was so intense 
to Banks in 1862 and to me in 1892 that we were able to glimpse it with 
small instruments (Fig 108). 1 * After examining the observations made by 
Secchi, Lockyer, J. Phillips, Banks, Rosse's observer, Kaiser, the Henry 
brothers, Green, Schiaparelli, Keeler, the Lick observers, Crouzel and 
myself, I have come to the conclusion that the changes in this region are 
periodical. The shaded area of Icaria was bounded by the Hyscus in 
1862, by Herculis Columnar in 1864 and again from 1877 to 1882, by 
the Hyscus once more in 1892, 1894, 1907, 1909 (Fig 109) and 191 1, 
and again by Herculis Columns in 1924 (Fig no). In 1926 its boundary 



• Maunder has carefully considered this observation, and is amazed at the visibility 
of Icaria in my o m io8 telescope. Icaria was then very shaded, as it was in 1909, and 
was not very different in appearance from Aonius Sinus. 



233 




Fig 108 karia seen as shaded, 2 September 1892, (o m -io8 refractor) 

lay between Herculis Columnae and the Hyscus. We see here an oscilla- 
tion with an irregular period, attributable to the changing fertility of the 
land. With the o'"-83, I see karia as very dark (Fig 80), and this was 
confirmed photographically by Lowell. In 1924 lcaria seemed to me to 
be a very smoky brick colour, and there was also a chestnut hue detect- 
able in it (c 344°)- In 1926 it was less dark. 

From Milan, in 1886, a white patch was seen persistently in this region, 
lcaria also sometimes whitens when near the edge of the disk, as Schia- 
parelli noted in 188 1-2 and 1886. 

On 14 October 191 1 I observed a beautiful white projection on the 
terminator here. It attained a height of 7km. 

ph/ethontis (S, 1877). Bounded by the Palinuri Fretum, the Simois, 
the Mare Siren urn and the Herculis Columnae. Phacthontis is very 
strongly shaded, though less so than lcaria. It is recognisable on Schrce- 
ter's sketches made as early as 1800. Banks and J. Phillips in 1862, 







b||P 


. 

™ 






• 


..-.-■ . 




Fig 100 (igoo) and Fig no (1924) Retreat of the dark materua! of 

lcaria toward the south-west 



234 



Kaiser in 1862 and 1864, and then many others showed Phaethontis as 
smoky. Lowell and Lampland photographed this shading in 1907 and 
1909, when with the o m -83 I always saw it as intense. In 1924 it 
appeared less noticeable than it had been in 1909, and less shaded than 
lcaria (Figs 109 and 1 to). In 1879 Schiaparelli glimpsed a large number 
of dark rays here, perpendicular to the Mare Sirenum. Phasthontis 
appeared leaden to Cerulli in 1898-9 (e = 130 ) and to me in 1909 
(e — 27 to 29 ); but in 1924 and 1926 it was purely a smoky-brick 
colour as seen from Meudon, with traces of chestnut (e = 344 and 
over). 

Phasthontis sometimes whitens when seen obliquely, especially in 
winter. Schiaparelli, in 1883-4, was tne ^ rst to rccor< ^ tnis effect. 

From Meudon, with the o'"-83, 1 observed a yellow projection on the 
terminator here on 5 January 1925, and another on 15 December 1926. 

dryadis PAI.US. A kind of diffuse marsh, seen by me in 1909, with the 
o m -83, in the SW part of Phaethontis (Fig 133). 

caralis pons. Blackish lake, noted in 1926 by Lyot from Meudon, to 
the S of the Mare Sirenum; I confirmed it (Fig 112). This is a recent 
formation. I saw it again in 1928-9. 

electris (S, 1877). This other smoky land lies between the Mare 
Chronium, the Scamander, the Mare Cimmerium and the Simois. It is 
recognisable on the drawings made by Schrceter in 1800, and was con- 
firmed by— among others— J. Phillips, Lockyer and Kaiser in 1862. To 
Schiaparelli in 1881-2 the NE part appeared even more shaded than the 
rest of the region. Lowell and Lampland photographed it as a grey area 
in 1907 and 1909. With the o m -83 in the latter year, I saw Electris as 
very grey; in 1924, it seemed to me to be less shaded than Phasthontis 
(Fig 113). Secchi saw it as red in 1862. From Meudon, in 1924, the 
colour of Electris seemed to be first rosy brick and smoky, and later 
slightly chestnut (e = 344 and over). The grey-brick tint was still visible 
in 1926. 

Electris sometimes whitens when seen obliquely, as Schiaparelli 
noticed in 1881-2. 



235 



eridania (S, 1877). Pentagonal land, shaded and variable, lying to the 
W of Eleetris, and at the antipodes of the Mare Acidalium. It is bounded 
by the Mare Chronium, the Xanthus, the Hesperus, the Mare Cim- 
merium and the Scamander. The shading in this region is seen on the 
drawings made by J. Phillips, Kaiser, Lockyer and numerous other 
observers. Lowell and Lampland recorded it photographically in 1907. 
During the whole of the 1 909 opposition, Eridania seemed to me to be 
decidedly bright, but no trace of this brightness remained in 191 1 or 
1924., when the whole land was again strongly shaded (Fig. 113). Sccchi 
found Eridania red. To me it was rosy and luminous in 1909; smoky 
rose-reddish in 1924, and somewhat chestnut after 11 October (e = i°). 
It was again greyish-brick in 1926. 

Eridania quite often whitens when seen obliquely; Galle, in 1839, was 
the first to record this^ phenomenon. 

It appeared protruding and whitish on the terminator on 7 December 
1926, in the great Meudon refractor. 

mare sirenum (S, 1877). This beautiful sombre region, lying about 
30° to the right of the Solis Lacus and touching the Mare Cimmerium, is 
bounded by the grey areas of Icaria and Phsethontis to the S. It is twice 
the area of our Caspian Sea, and is the easternmost of the three oblique 
seas, slanted almost SE to NW between longitude 140 and 260 . Its in- 
clination to the parallels of latitude is about 30 , according to Schiaparelli, 
and the 'beak" to the left makes an angle of almost 120 to its principal 
coasts to the N. It was first drawn by Maraldi in 1704, but it was not 
accurately shown until Schiaparelli observed it in 1877. Lockyer drew it 
as too small, Green and Lowell much too large. More than once in 1924 
I noticed that its extension in longitude was considerably less than 
normal— sometimes less than 6o°. The N extremity, or Titanum Sinus, 
is pointed; Trouvelot showed undulations on its banks, even more 
marked than those on the bay of Gorgonum Sinus. In 1909, with the 
Meudcn refractor, I saw the E point of the Mare Sirenum blunt and 
rounded, and the N coast, to -the right of this point, full of indentations 
(Fig 109). It seems that the general form of the Mare Sirenum (Fig 1 1 1) 
has not changed much over two centuries; but it was narrow in 1926 



236 



W 




Fig in The Mare Sirenum in ig24. fo m -Sj refactorj 

(e = 40°) ( Fig 1 1 2) and appeared extended toward the E, approaching 
Solis Lacus, on 4 February 1929 (e = m°). 

As Schiaparelli noted, Mare Sirenum is better defined on its N coast 
than on its S coast. This is due to the presence of the southern shadings. 
Its intensity is very considerable ; Beer and Msedler found it 'very black, 
particularly at its western extremity', toward Sirenum Sinus; 2 in 1862 
Lockyer found that it appeared darker than any feature he had previously 
observed on Mars. In 1877 Schiaparelli wrote that it was 'one of the 
most shaded (areas) on the planet . . . but . . . less dark than the 
Sinus Sabarus or the Margaritifcr Sinus'. 1 ' In 1879 it seemed to him to be 
less sombre; but in 188 1-2, more so. I never saw it as very dark between 
1892 and 1907, but it appeared quite sombre in 1909, as was photo- 
graphically confirmed. I found it less striking in 191 1, but stronger in 
1924 and 1926. In 1898-9 Cerulli and Rheden noted some darker patches 
here; Lassell in 1862, Husscy and Schajberle in 1892, and Campbell in 
1894 showed some brighter regions. With the o m -83 I have seen a great 
variety of tone in this sea. In 1909, for instance, the left coast was very 
sombre at its extremity, and so was the curved section, while the less 
shaded area between these two dark patches gave the impression that the 
Mare was cut up into segments — an effect also seen by Schiaparelli in 
1892. I also saw an island, in half-tone, toward Gorgonum Sinus (Fig 
109); the coast near Titanum Sinus was bordered by a darker shading 
which was not due to contrast; and in 1924 I distinguished a sombre 
interior patch, well to the S of Titanum Sinus (Figs 1 10 and in). The 
colour of the Mare Sirenum appeared blue to Seech i, green to Lockyer 



237 




Fig 112 Blackish spot which appeared to the south of the Mare Sirenum 
on I November IQ26. (o m -Hj refractor) 

in 1862 (e = i8 c ). The eminent observer Eddie noted it as bluish grey in 
1892 (e = 326°), and he also saw a dark brown shading along the N banks 
(e ■■ 327°); from 1898 to 1903 Molesworth saw it only as a bluish grey 
(e = ioo° to 220 ). In 1909 and 191 1, with the o m -83, I saw it as green 
(e = 8° and 42 ); then, in 1924, I distinguished pure green over the 
whole of the Mare, though after e = 345^ the sombre part to the E be- 
came lilac brown, and after 10 October (e = i°) the border of the N ; coast 
appeared to me to be carmine, while the rest of Mare Sirenum remained 
green and unchanged (Fig 1 13). In 1926 it was brown in the left section, 
green to the right (e = 20 ); then it became brown all over (e — 6o c ). In 
1929 (e - 107 ) it seemed to me to be wholly violet-brown, as was inde- 
pendently confirmed by Lyot. Thus Mare Sirenum is normally green, 
but can change to brown around e i', first to the left; then, between 
e = 6o u and about 107 , it becomes completely brown. However, these 
seasonal colour-changes are irregular. 

Various remarkable clouds have obliterated the Mare Sirenum from 
time to time. Among them may be cited that of October 1894; that of 
June and July 1909, when Maunder could not see the sea at all, while on 
14 July O'Hara drew it as very small, oval and deformed; and that which 
I observed in December 1924 and January 1925, effacing the Mare al- 
most completely. In 1879 Burton drew the Mare Sirenum deformed by 
a whitish streak. 

sirenum sinus. The E gulf of the Mare Sirenum, first represented by 

238 






Schrccter in 1800. With the o n, -83 I always see it broad and rounded. 

gorgonum sinus. This shallow gulf, with a rectangular point— also 
on the Marc Sirenum— was first shown on LasselPs drawings of 1862. It 
was well represented by Schiaparelli later. 

gigantum sinus. A bay on the Mare Sirenum, not very well marked. 
It was shown by Schiaparelli in 1877 and by Burton in 1879. In 1909, 
with the o'"'83, I saw it only as a slight salient (Fig 109). 

titanum sinus (S, 1 877). This is the N point of the Marc Sirenum, at 
longitude 170 . Maraldi I. was the first to draw this gulf, in 1704. In 1783 
Hcrschel showed it satisfactorily. It was shown as blunted on the chart 
by Beer and Mscdler. From Meudon, in 1924, 1 observed it under good 
conditions; it then seemed pointed, because the two beaks were turned 
toward the \, with the western of the two making a lesser angle to the 
meridian. The true point is thus sharper than a right angle (Fig 1 13). 

atlantidum sinus. Gulf at the extreme W of the Mare Sirenum, 
drawn by Rosse's observer in 1862. With the o m -83, 1 see it as rounded. 

10s insula. Triangular half-tone in the Mare Sirenum, near Gor- 
gonum Sinus. Campbell showed a bright patch here in 1894. From 
Meudon, in 1909, 1 observed it as triangular, better defined to the E than 
to the W (Fig 109); it was greenish, and showed a point toward Atlanti- 
dum Sinus. Since then I have seen it less well, but it was visible on 
4 February 1929. 

vorticis DEPRESSio. Sombre circular patch in the Marc Sirenum, at 
the end of Sirenum Sinus. To me it sometimes appears striking (Figs 1 1 1 
to 113), as it also did to Graff in 1924, when it had become brown (e = 
345 and over). 

fusca depressio. This is the darkest part of the Mare Sirenum, on the 
curve, to the E of Ios Insula. Lassell drew it in 1862, Eddie and Lowell 
in 1907, and I drew it in 1909, 191 1, and 1924 to 1929. With the o'»-83 it 
was very noticeable in 1924 (Figs in and 113), when it turned brown 
after e = 345 . From Meudon, in 1929, I followed it until the disk of 
Mars had been reduced to 8"-2. 

chim;eiue depressio. Dark patch in the Mare Sirenum, along the 
■coasts of Gigantum Sinus and Titanum Sinus. It appeared brown to 

239 



Eddie in 1892, carmine to me in 1924 (e = i° and over). 

sirenum deprkssio. Small dark patch in the Mare Sirenum. I observed 
it in 1924, about 1 1° to the S of Titanum Sinus. 

Atlantis 1 (S, 1877). Vague half-tone, separating Mare Sirenum from 
Mare Cimmerium; it disappears when high magnification is used. 
According to Schiapcrelli, Miedler drew Atlantis I in 1830. Lockyer 
indicated it feebly in 1862. From Milan it was seen as reasonably bright 
between 1877 and 1884, and also in 1890. I have never seen a trace of it 
with the o m -83. 

Atlantis II (S, 1877). Another half-tone, drawn by Schiaparclli pre- 
ceding and to the VV of Atlantis I; he saw it in 1877 and 1892, and, in 
diminished size, in 1879. It is a genuine feature at the W, where it corres- 
ponds to my Symplegades Insulae, 

mare cimmerium (S, 1 877). This great elongated and changeable sea, 
comparable in area with our Mediterranean, extends obliquely from the 
Mare Sirenum to the base of Hesperia. Drawn very early on by Hugens, 4 



-4c 



I ec.tr is ■; '■■ 





— ■■■ 


'■' ' r 'i^k 




■ 


Sffiigf; 




3o 














■ 








IsP^' 


10 






- 



















zio 


0.40 










. 


1 




it 


"1 dani ;v 


:s ; « 






. ■' \ ■ 












' 5-.^'. ';■*.• 


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Lxstrygop: 



to 

-3o 

t-»o 

; in 



)5o 



1 80 



1 J ' 3^B839HH 



11 

C M A 



Fig 113 Chart of I he Maria Sirenum and Cimmerium in 1924, with 

indication of the colour -changes observed. (o m -8j refractor) 

The shadings coming from the right indicate regions which turned 

chestnut in hue; those coining from the left turned to carmine; and the 

checkered areas showed change from green to lilac brown. The carmine 

does not seem to be due to atmospheric dispersion 



240 




it was more clearly represented by Maraldi I. in 1704 and 1719. Bianchini 
drew it even better in the latter year, making its form roughly that of a 
cigar, pointed to the right. Ill-defined on Herschel's drawings, and 
narrow to Arago in 1815, it was correctly shown as inclined to the 
parallels of latitude, but noticeably rounded to the W, on the drawings 
made by Beer and Masdler from 1830 to 1832. In 1858 Secchi observed 
it pointed to the NW, as did Kaiser, Harkness and Lockyer in 1862, 
Dawes in 1864, and Green and Dreyer in 1877. It is interesting to note 
that from 1877 to 1894 Schiaparelli always showed it rounded to the 
right; but this area is very variable. The following end was drawn as a 
narrow point by Cerulli from 1896 to 1899, slightly convex toward the 
SW; 1 confirmed this in 1909 with the o'"-83 (Fig 33). In 1 926-7, how- 
ever, the whole \V extremity, following the Cyclops, had disappeared! 
The Mare Cimmerium has four gulfs to the N and two to the S. 

In general, the intensity is less than that of the Mare Sirenum. How- 
ever, the VV part was drawn as very dark, large and rounded by Beer and 
Masdler in 1830, and in 1877 Schiaparelli found the whole sea looking as 
one of the darkest patches on Mars. Un-d dicker noted it as astonishingly 
dark in 1884. However, 1 have never seen it really sombre since 1892. The 
tone is not uniform. As early as 1832 Beer and Maedler recorded darker 
patches in it; so did Burton in 1879. Cerulli noted the same thing in 
1898-9, and had momentary glimpses of a system of patches — though 
this seems to be an exaggeration, as I was only able to confirm it in part. 
From Meudon, with excellent images, I noted at least two darker in- 
terior patches, a more intense streak along the N coast, and some com- 
plex half-tones to the E.* (Fig 113). Secchi saw the Mare Cimmerium 
blue in 1858 (e — 254 ) and in 1862 (e — 33 ). Lockyer noted it green, 
but this seems to be dubious. Eddie, in 1892 and 1907, saw it steely-blue 
and bluish green (e - 322" and 274 ); Molesworth, from 1896 to 1903, 
grey-blue (e — 6o° to 226 ). In 1909, with the o">-83, I saw it as a 
magnificent cobalt blue, without a trace of green (e = 2°); in 1924, 
Mmc. G.-C. Flammarion also saw the blue colour (e = 23°), and I noted 



■ The structure of numerous black points drawn by Comas Sola on Mare Cimmerium 
has never been confirmee! with the o™^, and is illusory. 



241 



the same colouration until the beginning of September, when Lsestry- 
gonum Sinus, Scamandri Sinus and Ariadnes Depressio passed succes- 
sively into lilac brown (e — 338° and over), while the N part of the Mure 
appeared carmine (e = i°) and the rest stayed a constant blue. The blue 
tint persisted in 1926, at least until December (e = 6o°); but in 1927 the 
Mare became, in part, brown (e = 94 ). In 1929 (e = 107 ) I found that 
the Mare Cimmerium appeared greenish-bluish. It seems to turn brown 
less markedly than the Mare Sirenum. 

This long sea is sometimes veiled by yellow clouds, which can deform 
it, enfeeble it, or even make it disappear. Thus from 10 to 31 October 
1894 it was almost completely obliterated. Flammarion found it ex- 
tremely pale on the 10th; on the 1 ith, Brown could scarcely see it; on the 
14th Stanley Williams could see only the W end; on the 15th, again 
according to Stanley Williams, there was only a trace of it; on the 16th, 




Fig 114 (1909) and Fig 115 (1926) Shortening of the following 
extremity of the Mare Cimmerium, observed in 1926 

Kempthorne could see only the W extremity; and Smart and Mee could 
not see it on the 21st. Patterson stated that the middle part of it was 
invisible, and that it was feeble at each end. On the 22nd Kempthorne 
and Henderson could not see it, and Barnard saw only the W end as a 
detached portion. On the 25th an observer as good as Maunder, with the 
o m 7i Greenwich equatorial, could see no trace of it, which was very 
surprising. Then, on the 28th, Barnard drew nothing whatsoever in its 
position! From Juvisy, I Yvas unable to see it on 30 September 1896. 
Eddie noted it as streaked by bright yellow clouds on 30 July J 907, and I 



242 



found it distinctly pale on 22 and 23 August 1909. In June 1924 there 
was considerable veiling, except over Cyclopum Sinus; and in December, 
with the o'"-83, I could scarcely sec it. At the time of the appearance of 
large white clouds, in October 191 1, the W part of the Mare was totally 
veiled. 

scamandri sinus. This gulf, at the S of the Mare Cimmerium, was in- 
dicated by Beer and Msedler in 1830. In 1909, with the o m -2t6 Juvisy 
reflector, it appeared to me as a dark round patch; with the o m 83 it 
seemed pointed. Again with the o'»-83, it seemed very highly developed 
in 1926 and 1929. After 13 October 1924, Baldet and I noted that it was 
lilac brown (e — 2°), and I saw this colour again in 1926 (e — 58 ). 

hesperi sinus. Also indicated by Beer and Msedler in 1832. This 
blunted gulf at the SW of the Mare Cimmerium was well drawn by 
Harkness and Lockyer in 1862. From Meudon, it always seems to me to 
be ill-defined. 

UESTROYGONUM SINUS (S, 1877), This is the most beautiful of the gulfs 
of the Mare Cimmerium. It lies on the N coast, about 30" to the W of 
Titanum Sinus. Beer and Msedler showed it in 1830 as an indentation in 
the sea, and Schiaparelli represented it well from 1877 to 1890; he con- 
sidered that between 1877 and 1879 it was partly merged with Atlantis II. 
With the great refractor I saw a detailed structure here in 191 1 ; to me the 
coast appeared obtuse at the F of the gulf and irregularly pointed to the 
W, forming Draconis Promontorium. This was confirmed in 1924 
(Fig 113), when I also found that after 5 September (e -^ 338 ) Lastry- 
gonum Sinus and the neighbouring part of the Mare to the W had be- 
come violet brown. I again saw this aspect in 1926 (e 58 c ). 

cyclopum SINUS (S, 1 877). Less marked than Lsestrygonum Sinus this 
second dark gulf, to the N of the Mare Cimmerium, was sketched by 
Beer and Msedler as a single indentation with Cerberi.Sinus. Lockyer, 
in 1862, showed it clearly; Schiaparelli also saw it in 1877, as did Trou- 
velot in 1884. Hussey drew it as very slender in 1892. To me it seemed 
definitely pointed in 1909 (Fig 33), and this was confirmed by Hale's 
beautiful photograph, I saw the gulf clearly in 1927 with a magnification 



243 



of 1250 on a 7"-8 disk of Mars. After n October 1924 (c — i°) all this 
region seemed to me to be carmine. 

cerberi sinus. A little less important than Cyclopum Sinus, this gulf 
on the N coast of the Mare Cinimerium was also first indicated by Beer 
and Maedler;"it was then drawn by Lockyer in 1862, Schiaparelli and 
Burton in 1879, and Trouvelot in 1883-4. Husscy saw it as slender in 
1892, as did Millochau in 190 1 and 1903. To me it seemed similar to 
Cyclopum Sinus in 1909 (Fig 33); in the same year it was photographed 
by Hale. In 1924 it and the neighbouring coast appeared carmine 
(e = i'). 

Triton is sinus. This gulf is made up by the following point of the 
Marc Cimmerium. Observations made by Cerulli between 1896 and 
1899, Millochau in 1901 and Eddie in 1907 confirm my own in showing 
it as pointed. However, in September 1926 no trace of it remained! 
(Fig 115). To me, this whole region appeared carmine in 1924 (e = i°). 

symplegades insula. Irregular half-tones, situated in the E part of 
the Mare Cimmerium, to the left of Laestrygonum Sinus. As early as 
1864, Kaiser drew here a feeble smoky patch in the Mare. Green observed 
something analogous in 1877, as did Schiaparelli, with the Atlantis II, 
from 1877 to 1882. Schaeberle drew an island here In 1892, and Cerulli 
showed the half-tone in 1896-7. With the o m -83 in 1909, 1 saw here three 
smoky yellow masses, touching each other, extremely irregular and 
broken up. 1 confirmed them in 191 1 and 1924 (Fig 113). They were 
more extended in 1926. In 1877, according to the drawings made at 
Milan, Atlantis II extended as far as Lsestrygonum Sinus. 

cimmeria insula (S, 1 88 1 -2). Half-tone, very probably due to con- 
trast. It was recorded at the time of the 'geminations', and had the form 
of a comet, with the head turned toward Tritonis Sinus. Schiaparelli 
glimpsed it in 1881-2, in the Mare Cimmerium. In 1911 Graff drew the 
whole interior of the Mare as a half-tone. 

ARIADNES DEPRESSIO. Small dark patch in the Mare Cimmerium; I 
noted it in 1909 to the SE of Symplegadcs Insula;, and I saw it as violet 
lilac in 1924 after October 14 (e = 3 ). The same hue was seen in 1926 
(e = 58 ). 






atauantes depressio. Another similar patch in the Mare Cimmerium, 
to the XW of Scamandri Sinus. I noted it in 1909, and I made it violet 
brown in 1926 (e = 58 s ). 

ORESTIADUM depressio. Sombre part of the Mare Cimmerium, to the 
SE of Cyclopum Sinus, along the coast of /Foils. The shading here was 
first drawn by Burton in 1879, and I confirmed it in 1909. 

hesperia (S, 1877). This vast shaded peninsula, of variable intensity, 
extends obliquely from Eridania to Amenthes, and separates the Mare 
Cimmerium from the Mare Tyrrhenum. It was shown on Bianchini's 
drawings made in 1719 (Fig 1 16). 5 Its form, very difficult to draw, was 
represented only inadequately by Beer and Maedlcr in 1830, by Lockyer 
and Kaiser in 1862 and by Dawes in 1864. Schiaparelli represented it as 
narrow to the S, broad and curved back toward the N. In 1909 I saw it 
noticeably broad in the middle, narrowing toward the \ (Fig 33), and 
this was confirmed on Hale's plates. The greyness here was recognised 




Fig r/6 The peninsula of Hesperia, seen by Bianchini in IJH) between 
the Mare Cimmerium am! the Mare Tyrrhenum 

by Beer and Maedlcr in 1832, and it was also indicated by Lockyer and 
Kaiser in 1862 and by Kaiser in 1864. Dawes did not see it. In 1877 it 
seems to have been of reduced intensity, because Green, Schiaparelli, 
Dreyer, the Henry brothers, N'iesten and Harkness drew Hesperia as 
bright. In 1879, from Milan, it was seen as patchy to the SE. In 1881-2 
Boeddicker and Schiaparelli drew it as light grey; in 1888 and 1890 
Schiaparelli found it smoky up to the Triton, and so did Keeler in 
1 892. Barnard drew it as very narrow in 1 894. To me it always appeared 
very considerably shaded from 1892 to 1916, and particularly so from 



244 



245 



1924 to 1929 as seen from Meudon, though with the o ,n -83 I could 
only just see it in the latter year. Hale and Barnard photographed the 
shading in 1909. In 1883 4 Schiaparelli saw Hesperia as billowy, and 
as if covered with a vast number of small dark patches. 'The colour was 
seen as yellowish from Milan in 1877 (e — | 350°); red, extremely dark, 
in 1888 (e — 2iz° to 253 ). At this time Holdcn saw it as whitish red. In 
1909, with the o" l -83, 1 saw it as violet grey (e — 35S ) ; in 191 1, I found 
it grey (e = 37 to 56 ); in 1924, greyish, and later always cobalt blue 
(e = 359 to 1 8°). In 1926 it was blue (e = [4°), and in 1927 and 1928 
simply grey, with no blucness (e = 95 and 86°). 

On 14 October 191 1 Hesperia appeared to me to be covered with 
white, cloudy masses of the type already described. This peninsula does 
not often brighten when near the limb; however, the effect was recorded 
by Schiaparelli in 188 1-2, and I confirmed it, though only once, in 191 1. 

On 10 June 1892 Perrotin saw here a brilliant projection on the 
terminator; on 6 September 1894 Stanley Williams saw another, this 
time in the S part of Hesperia; and on 27 October 1924, van Biesbroeck, 
using the Yerkes 1 m -02 telescope, is said to have observed an enormous 
whitish protuberance, very high and completely detached from the 
terminator. 

HYRIA lacus. Vast isolated, complex lake on Hesperia. Traces of it 
were shown in the drawings made in 1877 by Cruls. Burton drew a tri- 
angular peninsula here in 1879; Schiaparelli saw only a canal, which was 
double in 1890 and seen as single in 1894. From Juvisy, in 1886-7, I 
observed Hesperia as notched in the middle, and Cerulli glimpsed a 
canal. In 1907 Buchanan drew an ill-defined shading in this area. In 1909, 
with the oh>-83 and using averted vision, I saw a large lake, extremely 
irregular and broken up, composed principally of a complex mass to the 
W, together with an indented streak directed toward the SE (Fig 33). 
This lake was isolated. Several days later, Hale and Barnard photo- 
graphed it. To me it then appeared confused, but with a magnification 
of 1250 on the o M,, 83 in 1927 I saw it on a Martian disk only 7"-8 in 
diameter. 

MEM NOMA (S, 1877). This continental region is bounded by the Mare 

246 



Sircnum to the S, the Gigas to the W, the Eumenides to the N, and the 
Sirenius I to the E. It is very luminous in the S, smoky in the N (Fig 
113); it makes up the principal declivity of the Mare Sirenum. The 
bright, sterile part close to the Mare Sirenum was shown on Dawes' 
drawings of 1864, and on those made in 1877 by Cruls, Schiaparelli and 
Lohse. The lumimous part was again seen from Milan in 1879, and then 
by Mole-sworrh from 1896 to 1903. 1 have almost always been able to 
observe it from Meudon, and the distinguished observer Graff indicated 
it in 1924. The penumbra to the N was represented by Schrcctcr in 1800; 
in 1909 I showed, as Schiaparelli had done thirty years earlier, that it 
was produced by the broadening, toward the bottom, of the complex 
streaks or tributaries of the Sirenius I and the Gorgon. Memnonia 
appeared red to Seech i, Holden and Lowell. In 1924, with the o m -83, I 
showed it a vivid rose colour, with a reddish tint. 

Memnonia sometimes whitens when seen obliquely, as was noted by 
Schiaparelli in 1877. 

I observed a glittering projection on the terminator at Memnonia on 
15 December 1926, at long. 145 , lat. 15 S. 

lumen. Bright patch to the NE of Titanum Sinus; I saw it from 
Meudon in 1909, 191 1 and 1924. To me it then appeared creamy yellow; 
it extended along the coast, beginning near Gorgonum Sinus, and 
broadening out into an oval spot near Titanum Sinus (Fig 1 13). 

sirenum PROMONTORIUM. Pointed cape of Memnonia, lying on the 
curve of Mare Sirenum. I saw it in 1909 with the o m -83 ; the coast to the 
E was cut up into saw-teeth (Fig 109). 

aquil/e fons. Small dark patch; I glimpsed it in 1924 to the N of 
Sirenum Sinus (Fig 1 13). 

mesowea. This land makes up part of Schiaparelli's original Amazonis. 
It continues the shaded, infinitely complex part of the continent at the N 
of the Titanum Sinus. It is bounded to the W by the Tartarus, and joins 
Medusae Fons to the E. Its form is that of a very irregular triangle, and 
with the o m -83 this greenish penumbra has always attracted my atten- 
tion since 1909. With beautiful images from Meudon in 1924, Mesogaea 
appeared to me to be composed of a very large number of small, dark 
greenish patches, each of about the same size (e = 2°) (Fig 113). 



247 



In 1929 (e = 107 ) this region was a very striking chest nut -reddish- 
vermillion. 

medusa fons. Beautiful lake, to the NE of Titanum Sinus. Lowell 
seems to have indicated it in 1907. I observed it in 1909 and 191 1, and 
again in 1924. I have almost always found it striking ( Fig 113), except on 
one occasion when it was covered with yellow clouds. However, I was 
unable to see it in 1926, though it was again visible in 1929. 

zephyri fons. Small lake which I noted in 1909 and 191 1. It is NW of 
Titanum Sinus, and closer to it than Medusae Fons. I found Zephyri 
Fons easy in 1924 (Fig 1 13), but difficult in 1926. It is curious that van 
Biesbroeck drew neither Zephyri Fons nor Medusae Fons in 1924, 
although he observed the region under superb conditions with the great 
Yerkes refractor. 

Jubar. Bright creamy patch, irregularly circular, which I recorded in 
1924 to the W of Titanum Sinus and some way from the Mare Sirenum 
(% 113). 



zephyri a (S, 1877). Desert continental region, bounded by the Mare 
Cimmeriuni to the S, the Lssstrygon to the W, the Orcus to the N and 
the Tartarus to the E. As with Memnonia, it is bright and featureless to 
the S, and shaded to the N (Fig 113), as was noted by Bceddicker in 
1 88 1-2. In 1896-7 Cerulli saw the lower peninsula studded with numer- 
ous shaded nuclei. In 1924, I found that the grcyness was bounded by 
the knotty curve of the Avernus. Graff also showed this at the same time. 
In 1927 I was able to follow the greyness up to the time when the dia- 
meter of the disk of Mars was only 7*7. Secchi saw Zephyria as red ; 
Bceddicker as dark orange to the S, slightly greyish to the N. To me, in 
1924, the S part seemed pure rose in colour. 

Zephyria sometimes whitens when seen obliquely, as was shown on a 
drawing made by Schroter as early as 1800. 

On 16 March 1929 I saw an immense dark yellow protuberance above 
Zephyria; it was completely detached from the terminator. It was strik- 
ing, and rose to at least 30km. above the surface of Mars. I notified 
Frappat, who also saw it with the great refractor. 

aqu/e apollinares (L, 1 894). This is a lake of some size, first drawn 

248 



by Hussey in 1892 in the middle of Zephyria, and confirmed by Moles- 
worth and Phillips in 1896-7 and by Molesworth in 1900-1. Lowell 
noted it in 1894 and 1907, G. Fournier in 1909. I observed it from 
Meudon in 1909 and 191 1, and to me it appeared very well-developed in 
1924, on the Avernus (Fig 1 13). It was pale in 1926. 

DiA.N/E fons. Small lake on the Avernus, to the SE of Aquae Apolli- 
nares. I saw it in 1924, with the o ,,u 83. 

lyr^e FONS. Yet another small lake on the Avernus, to the W ot 
Diana; Fons; I observed it from Meudon in 1924. 

jeous (S, 1877). Desert land, bounded by the Marc Cimmcrium to the 
S, the Cyclops to the W, the Cerberus to the N and the Laestrygon to the 
K. As with Memnonia and Zephyria, it is bright and arid to the S, shaded 
to the N (Fig 1 13). A half-tone was drawn here by Gallc in 1839, and 
then by Lohse in 1873, Bceddicker in 1881-2, and others. From Meudon, 
the shading always seems to me to begin at the Anta:us; I saw it in 1927 
on a disk only f-j in diameter. Secchi saw /Eolis red; Niesten said that 
it had reddish reflections; Bceddicker called it reddish. I saw it very red 
in 1909. In 1924, 1 was struck by its pure rose colour. 

In 1888 Holden found this region brilliant when on the central 
meridian. /Eolis sometimes whitens when near the limb, a pheno- 
menon first indicated by Schrceter in 1800. 

draconis promontorilm. This is the cape of JEolis in the Mare 
Cimmcrium to the right of Laestrygonum Sinus. With the o m -83, I saw 
it as pointed in 191 1 and 1924. 

antjei fons. Lake on the Antaeus, near the Laestrygon, which I saw 
in 1909, 191 1, 1924 am! 1926 with the o m 83. 

crucis fons. Another cut-up lake, to the NW of Antaei Fons, and 
noted by me at the same oppositions. 

lupi fons. Third irregular lake on the Antaeus, more important than 
the preceding two, and which I glimpsed from Meudon at the same 
times. 

flor/e fons. Small irregular lake on the Laestrygon, which Lowell 
drew in 1907 and called 'Jol\ and which I observed with the o'"-83 in 
1909. 

249 



avlonis fons. Another lake on the Laestrygon, further N, which 
Lowell drew in 1907 and named 'Aulon'. As with the others, I glimpsed 
it from Meudon in 1909. 

scorpii palus. This is a very broken-up marsh, composed of two un- 
equal parts. It lies to the SE of Cerberus I. With the o ni -83 I observed it 
in 1909, and less well in 1924. 

cyclopia. Small continental region, contained between Cyclopum 
Sinus and Cerberi Sinus; in 1909 its lower boundary was accurate. It is 
flanked by the Cyclops and the Cerberus II. Cyclopia is very strongly 
shaded-off; it showed great changes at the times of the great develop- 
ment of the Cyclops between 1783 and 1800, as is seen from the sketches 
made by Herschel and Schroter (Figs 131 and 132). Mssdler showed 
nothing particular here between 1830 and 1841, but Secchi drew a 
penumbra in 1858 and 1862. Then, in 1881-2, Bceddicker drew the space 
between the Cyclops and the Cerberus II as greyish; this is also how it 
was photographed by Hale in 1909. With the o m -83, in 191 1, 1 saw feeble 
shading here; but in 1924 the surface was bright, except on 2 August, 
when it appeared partly smoky. There was shading here in 1926. 

CYCLOPUM fons. This is a small lake to the N of Cyclopum Sinus, 
probably indicated by Schaeberle in 1892 and by Lowell in 1894, who 
called it 'Lucus Angitiae'. Millochau drew it excellently in 1901 and 
1903. Lowell saw it again in 1907, and so did G. Fournier in 1909. I saw 
it in 1924 (Fig 113). 

^thiopis (S, 1877). Continental desert region, but not completely 
infertile. It lies between the Mare Cimmerium to the S, the ^Ethiopis to 
the W, the Hephaestus to the N, and the Cerberus II to the E. The 
albedo here appears less than those of the lands bordering the .Maria 
Cimmerium and Sirenum further to the E. The penumbra in this region 
was represented by Kaiser in 1862, by Cruls in 1877 and by Kempthorne 
in 1898-9. Schrceter drew a vast, shaded, sombre triangle, comparable 
with the Syrtis Major, in 1800 (Fig 132)*. The soil here is variable, and 
becomes temporarily fertile. In 1924, from Meudon, /Ethiopis presented 

• See below, in iht description of the Cyclops. 
250 



a rose hue until 27 June; it began to darken unevenly after 2 August, 
with a part of Amenthes, and the darkening spread until it joined the 
shading of Libya (Figs 117 and 118). Then, on 8 October and the 




Fig J/7 (2 August) and Fig 118 (5 September) Overflowing 0/ the 
penumbra on JCthioph and Amenthes in 1924. (o m -83 refractor) 

following days, I saw here a vast greyish area, clearly rose or carmine, 
making the form of a V pointed toward the Hephaestus, and recalling a 
paler version of Schitwcr's shaded triangle (Fig 1 19). The country here 




Fig 11a Mars tvith two Hourglass Seas, as in 1800. Observation made 
on 8 October 1024. (o m -83 refractor) 

was still shaded in 1926. Secchi noted a red colour in these regions, 
streaked with more vivid points; Breddicker saw a reddish tint; Le 

Coultre, clear rose. 

iEthiopis was partly covered with white clouds, as seen from Meudon, 
on 24 October 191 1 ; and Schrceter's sketches made in the 18th century 
show that it sometimes whitens when near the limb. 

CERBERI fons. On the photographs taken by Lowell and Lampland in 
1907 I noted a very small lake to the SW of Pambotis Lacus; in 191 1, 

251 



from Mcudon, I observed it as blackish. 

scotitve pons. Small lake, lying to the S of Hephaestus, which Lowell 
observed in 1903 and 1905 and called 'Scotitas'. Eddie confirmed it in 
1907. In spite of its apparent smallness, it is five times larger than our 
Lake of Geneva. 




/' / 



Fig 120 Nodus Gordii, seen across a layer of yellow clouds veiling the 
seas, 31 December KJ24. (o m -8j refractor) 

nodus gordii (S, 1881-2). Vast shaded region, diffuse and feeble, 
about 1500km to the N of Sirenum Sinus, and lying at the antipodes of 
the Syrtis Major. Beer and Masdler observed it in 1837 and 1839 as a 
light penumbra, and Dawes seems to have drawn it before 1867. Trou- 
velot and Schiaparelli studied it in 1877. From Milan it was intense in 
1 88 1 -2, very smoky and ill-defined from 1886 to 1890. To me it appeared 
complex and essentially diffuse between 1894 and 1897, and also in 1909. 
At the time of the great pallor of December ^24, Nodus Gordii 
appeared, from Mcudon, to be darker than any other patch! (Pig i 30 ) 
The greyness was feeble in 1926. In X888 Schiaparelli noted that this 
diffuse shading was better seen under oblique conditions than when on 
the central meridian; this was confirmed by Cerulli in 1898-9 and myself 
m 1924 and 1929. In February 1929, from Meudon, I saw Nodus Gordii 
as red. 



252 



PHRYGius LACUS. Small dark patch on the Eumenides, toward the 
meridian of Gorgonum Sinus. It was observed by Gale and Hussey in 
1892, Lowell in 1894, Douglass and Cerulli in 1898-9, Molesworth from 
1896 to 1903, Lowell from 1900 to 1907, Eddie in 1907, and G. Fournier 
and Hawkes in 1909. 

LOCOS WiBXCM (L, 1894). This is another lake of the Eumenides, to 
the W of Phrygius Lacus. (rale observed it in 1892, Lowell in 1894, 
Molesworth from 1896 to 1903, and Dobbie in 1907. I glimpsed it 
vaguely in 1909 and 1924. 

urani/k pons. Third lake on the Eumenides, to the right of Phyrgius 
Lacus and Lucus Maricas. It also was observed by Gale in 1892 and by 
Lowell in 1894, who called it 'Utopia'. Molesworth drew it in 1896-7, 
Cerulli in 1898-9, Lowell again in 1903, Eddie in 1907, and myself 
vaguely in 1909 and 1924. 

ammonii PONS. Fourth lake on the Eumenides, to the W of the others. 
Schiaparelli drew it double in 1888, and Stanley Williams saw an ex- 
tended shading-off here in 1890. Subsequently Gale noted it in 1892, as 
did Lowell in 1894, who called it 'Ammonium'. Molesworth and I saw it 
in 1896-7; Douglass, Cerulli, Phillips and Molesworth observed it in 
1898^9, and so did Attkins in 1900-1, Molesworth from 1900 to 1903, 
Eddie and Lowell in 1907, and Fournier, Hawks and myself in 1909. 
With the o'"-83, I found it very confused and difficult in 191 1 and 1924. 

castalia pons (L, 1 894). Lake on the Orcus, drawn by Ix)well in 1894 
and confirmed by Molesworth in 1896-7 and very vaguely by myself in 
1909. 

kibes fons. Very small lake of the Orcus, to the right of Castalia Fons. 
Lowell saw it between 1894 and 1897, and called it 'Hibe'. 

These six latter lakes seem to have been more intense thirty years ago 
than they arc now. 

tribium CHAKONTis (S, 1 88 1 -2). This is one of the most important 
inland lakes on the planet, and is twice as large as our Sea of Aral. It lies 
to the E of Elysium. Its form is irregularly triangular, and it is very 
variable in intensity; it may either remain invisible or else appear black- 
ish. It is found on a sketch made by Herschel in 1781, and Schroeter 



253 



drew it in 1798. Beer and Maedler did not show it at all in 1830, but it 
was seen feebly in 1832; then, in 1837, Galle once saw it as extremely 
intense. In 1839 Gallc made it very sombre; Maedler, in 1841, described 
it as broad and diffuse. It is curious that nobody saw it from 1858 to 
1864. Backhouse found it very feeble in 1869 and 1871, but less so in 
1873. Again, in 1877, Trouvelot, Cruls and Green did not see it at all; 
Schiaparelli said that it was pale, and to Flammarion it was invisible 
before 26 October. Trouvelot saw nothing of it in 1879, while Burton and 
Schiaparelli noted it as feeble. In 188 1-2 Beeddicker sometimes saw it as 
intense, but Schiaparelli could distinguish only a cross-roads of canals. 
From Milan, he glimpsed it in the form of double bands leading toward 
the Orcus; in 1886 he described it as single and pale; in 1888, doubled 
bands following the Erebus; and in 1890, double toward the Orcus, 
Hussey drew two patches here in 1892, while, with Lemoine, I managed 
to see the Trivium with an o m io8 refractor (Fig 121). In 1894 I noted it 




Fig 121 The Trivium Charontis, seen on 
(O m -ioH refractor) 



August 1892, 



as pale; on 5 November 1896 Flammarion found it well-developed and 
sombre; and five days later I saw here two round black patches (Fig 123), 
of which the northern could well have been Stygis Pal us. In letters to me, 
Schiaparelli and Lowell confirmed this aspect. On 20 December 'the 
Trivium Charontis was double, as you have seen it,' the Italian astrono- 
mer wrote. To me, in 1898-9, it was still very dark; in 1900-1, less so. In 
1903 Millochau drew it as small, but very intense; in 1905 and 1907 1 saw 
it as decidedly sombre. Lowell and Lampland photographed it with 
success at this time. In 1909 I saw it as pale, below lemon-yellow clouds; 
in 19 1 1 , from Meudon, it Mas darker, and this was also the case in 191:3- 

254 





r-r~ 






















■■■ .jj&W 






w 








in 






10 00 










I . 



















Fig 122 Extraordinary darkening of the Trivium Charontis, Cerberus and 
Pamboth Lacus, in 1924. (o m -8j refractor) 

4, though I recorded it as feeble in 1915-6. Briault noted it is moder- 
ately intense in 19 18. G. Fournier, Quenisset and Danjon again found 
it very dark in 1920; Danjon, paler in 1922. In 1924 I found it very 
feeble in June, but Quenisset called my attention to the fact that it was 
extremely dark on 1 August, and, with the o m -83, I confirmed this after 
2 August (Fig 122). In spite of several clouds, this unprecedented in- 
tensity was maintained almost until November. The lake was again very 
pale in 1926, and rather small and feeble in 1929. 

Lowell saw the Trivium triangular in 1896-7, elongated toward the 
Orcus and with a small lake round one of its angles; there was another 
lake in the middle of the S side. In 1899 Stanley Williams also saw it as 
triangular. 

Yellow clouds can partly explain the invisibility or temporary enfeeble- 
ment of the Trivium Charontis in 1830, 1858-64, 1877, etc. However, 
the patch itself also changes; the exceptional development in 1839 and 
1896, and above all in 1924, is certainly due to temporary darkening of 
this remarkable feature. 

TRivn pons. Small lake to the SW of Trivium Charontis, drawn by 
Lowell between 1896 and 1907. 

stygis lacus. Lake to the NNVV of the Trivium, which, when well- 
developed, probably causes the apparent doubling of the Trivium itself, 
as glimpsed by me in 1896 (Fig 123). Schiaparelli and Lowell drew it at 
the same time. Cerulli showed it in 1898-9, Molesworth from 1900 to 
1903, and G. Fournier in 1911. 

255 



pambotis lacus (C, 1 896-7). This is an important but very variable 
lake, to the S of Elysium. It was indicated by Boeddicker in 1 88 1-2, but 
escaped the notice of Schiaparelli until 1890, when to him it appeared 
extended and intense. It was not seen at the Lick Observatory in 1892 or 
1894, which is strange; but Lowell noted it in the latter year. Moles- 




Fig 123 Trivium Charontis and Stygis Lacus seen as black circles 

despite their eccentric position on the disk, on 10 September 1896. 

(0^-240 refractor) 

worth drew it as triple in 1896-7; then Molesworth and Cerulli in 1896- 
7, Brown, Douglass and Cerulli in 1898-9, noted it as extended, though 
at this time I could see nothing abnormal (Fig 124). Later, in 1900-1, 
Lowell and Molesworth saw that it had again become an important 
feature. It was further developed in 1903, and Millochau made it even 
more important than the Trivium Charontis. In 1905, from Juvisy, 
Benoit noted it as very much in evidence. In 1907 it was almost as exten- 
sive and dark as the Trivium; observations by Jarry-Desioges, G. 




Fig 124 Antoniadi, 1899 (0^24 refractor) and Fig 125 Givin, 190? 
(o m -oqi refractor) The Pambotis Lacus, very enlarged in 1907 



256 



Fournier, Eddie, Givin, N angle, Shearer and Tornquist all agree on this 
point, and Givin saw it clearly with a very small refractor of aperture 
om-ogi ! (Fig 125). Certainly Givin's result was excellent. From Meudon, 
I found the lake less important in 1909 and 191 1, and this was also the 
case in subsequent years; but on 1 August 1924 Quenisset found it 
exceptionally large and black. I was able to confirm this, with the o m -83, 
from the following day (Fig 122). It appeared extremely broken up, a 
little smaller than Trivium Charontis. Its extraordinary intensity was 
maintained, though with some variations, almost until November. It was 
suspected in 1926. 

morpheos lacus. Lying at the NW angle of Elysium, this lake was 
drawn by Schiaparelli and Denning in 1888 and by Schiaparelli in 1890. 
It was again observed by Cerulli, Phillips and Brown in 1898—9, Millo- 
chau from 1900 to 1903, Eddie in 1907, Graff and myself in 191 1, G. 
Fournier in 1913-4, and Briault from 1916 to 1918. Millochau saw it as 
triangular, and to me, with the o m -83 in 191 1, it seemed to be 6 s broad 
(Fig 126). 

hecates lacus (S, 1 888). This is a lake similar to Morpheos Lacus, at 
the NE angle of Elysium. Bceddicker drew it in i88r-2, and to Schia- 
parelli it seemed dark in 1888 and 1890. Phillips saw it in 1898-9. I 
observed it from 1898 to 1901, from Juvisy, and in 191 1 from Meudon 
(Fig 126). G. Fournier drew it in 19 13-4, and Millochau saw it as tri- 
angular, like Morpheos Lacus, in 1 900-1. 

elysium (S, 1877). Great pentagonal desert, luminous rose in colour, 
to the N of the Mare Cimmerium. Its dimensions, comparable with 
those of the Belgian Congo, are vastly exaggerated by diffraction in small 
instruments. It is strange that neither Herschel nor Beer and Midler 
showed it. Galle observed it well in 1837 and 1839, and Secchi noticed 
its high albedo in 1858. Yet nobody drew it in 1862, nor in 1864. Schia- 
parelli, in 1877, saw no more than the vague top part of it, and it was not 
until 1886 that it was accurately drawn. The whiteness of Elysium was 
well rendered by Holden, Schiaparelli and Perrotin in 1888, but it is 
curious that I was never able to see Elysium at all until 1894. Oh the 
other hand, I was struck by its vivid brilliance between 1896 and 1899, 



257 



and also in 1903, with Benoit. In the latter year Millochau found that in 
March Elysium was almost as resplendent as the snowy polar cap, but by 
May it had again become reddish. In 1907 Lowell and Lamp land photo- 
graphed it as very slightly less shaded than the neighbouring countries. 
Then, in 1909, I saw it veiled by lemon-yellow clouds. In 191 1, with the 
o m -83, 1 saw it whitish (Fig 126). The aspect was much the same in 




Fig u6 Elysium, 14 October 1911. (o m -8j refractor) 

1913 4, but in 1915-6 Elysium had become difficult to see. Quenisset 
observed It as brilliant yellow in 19 18; Danjon saw it bright in 1920. 
Then, in 1924, 1 saw it as white until October. The pentagon was ill- 
defined in 1926. Schiaparelli made Elysium yellow, Perrotin rose or 
white, Le Coultre pure rose. 

This exceptionally arid region, comparable with some of the whitish 
expanses of the Sahara, often glitters when seen obliquely, as was shown 
by Schroter as early as 1800. In 1896-7 Cerulli sometimes saw it as 
brilliant as the polar snow. 

albor. The brightest part of Elysium, to the W of Trivium Charontis. 
I often noted it as brilliant from 1896 to 1903. 



amazonis (S, 1877). Originally, this name indicated the land con- 
tained between the Titan, the Eumenides and the Gigas; but after 1882 
it was restricted to the country to the N of the Eumenides. This is a vast, 
smoky continent, as was first shown by Maraldi in 1704, and as it has 
been seen by many others since. From Meudon I have almost always 
observed Amazonis as slightly greyish; once, with the o"'-83 in 1909, I 
saw an infinitely complex and irregular structure, made up of undulating 

258 



filaments and small dark nuclei. Bceddicker noted a reddish-grey tint 
here; Cerulli saw it red. 1 made it smoky red in 1924; in 1929 it was 
ruddy chestnut- vermilion, more shaded than Arcadia. 

Amazonis does not often whiten when seen obliquely, but the pheno- 
menon was seen by Cerulli from 1896 to 1899, and, among others, by 
myself between 1903 and 1924. 

liuiLis fons (L, 1894). Small lake, seen by Lowell from 189410 1907 
to the N of \odus Gordii. 

bandusl;e fons (L, 1894). Another small lake, drawn by Lowell to the 
NW of Bib! is Fons, and on the same dates. 

ferentin/e lucus (L, 1894). Yet another lake, to the NW of Ban- 
dustee Fons, seen by Lowell between 1894 and 1907, and by Attkins in 
1900-1. 

titanum fons. Small lake to the X of Ammonii Fons, drawn by 
Lowell in 1896 and named by him 'Moreh'. Molesworth showed it from 
1900 to 1903, Lowell again in 1903 and 1907, and Eddie in 1907. 

hyperuei fons (L, 1 894). This is probably another small lake, ob- 
served by Lowell between 1894 and 1899 to the NW of Titanum Fons. 

aphnitis fons. Yet another small lake, to the N of Titanum Fons. 
Schiaparelli saw it double in 1888. Lowell observed it between 1896 and 
1907, and Molesworth from 1896 to 1903. 

AACANtt palus. Extensive marsh to the NE of Aphnitis Fons. It was 
seen by Cerulli in 1898-9, and by Lowell from 1900 to 1905, who called 
it 'Semnon Lacus'. Subsequently it was seen in 1903, 1905, 19 13 and 
1916 by Phillips, one of the very best observers of our time. 

euxinus LACUS. This is a considerable shading, preceding Propontis I. 
Perrotin, in 1888, showed it as large as Propontis I, and this was con- 
firmed by Douglass and Cerulli ten years later. Lowell called it "Propro- 
pontis' in 1 900-1 , when it was also observed by that very skilful observer 
Attkins and also by Molesworth. Generally speaking, Millochau, 
Denning, Gale, Lowell and Molesworth drew it dark in 1903, and Lowell 
again showed it in 1905 and 1907. G. Founder, Phillips and Thomson 
saw it in 19 13-4, and Phillips drew it again in 1916. It is generally 
smaller than Propontis I, to which Danjon saw it joined in 1920. With 



259 



the o m -83 I saw it clearly in 1929, when it appeared sombre, bluish, and 
less extensive than Propontis I. 

castorius lacus (S, 1888). This lake is more important than Euxinus 
Lacus, and lies to the N of it. In 1888 Schiaparelli found it as dark as 
Propontis I, but rather smaller (Fig 144); however, he did not see it at 
all in 1890. Its existence was confirmed by — among others — Cerulli in 
1896-7, Molesvvorth between 1900 and 1903. Millochau, Denning and 
Lowell in 1903, Lowell in 1905 (when the lake was often veiled), Eddie 
in 1907, G, Fournier, Phillips and Thomson in 1913-4, Briault in 
1915-6, and Danjon in 1920. 

artynia FONS. Small greyish condensation on the Eurotas, which pre- 
cedes Castorius Lacus. It was seen by Cerulli in 1896-7, Molesworth in 
1903, Ward in 1905, and G. Fournier in 1913-4. 

propontis I (S, 1 88 1 -2). This is a large dark lake, a little less impor- 
tant than Trivium Charontis, and isolated in the wildernesses a long way 
from the nearest sea. It is elongated along the parallel of latitude, and 
lies to the NNE of Trivium Charontis. Secchi was the first to draw 
Propontis I, in 1858, when it was pale; Schiaparelli and Burton observed 
it in 1879. Schiaparelli and Bceddicker showed it as intense in 1881-2, 
and it was studied from Milan until 1890, generally appearing rect- 
angular. It seemed more sombre to the E in 1883-4 ant ^ '886, narrow 
in 1888 (Fig 144), and often very black and double in 1890. In the latter 
year, Giovannozzi glimpsed it with an o m - 108 telescope. Cerulli observed 
it well from 1896 to 1903, from juvisy and Paris (Fig 127). In the latter 




Fig /_V Propontis I and II, 18 March KjOJ. (o m -2i6 reflector J 



260 



year Millochau described it as feeble; Gale showed it as sombre in 1905. 
It appeared pale from Meudon in 191 1, floccular from 1913 to 1916. 
Phillips and Thomson drew it dark in 1918, Danjon and Qucnisset feeble 
in 1920. Lyot and I had a good view of it on 28 January 1929; it was 
elongated in an E-VV direction, sombre, and of a striking indigo blue. 

Propontis I is nearly 3600km from Titanum Sinus, 4500 from Mare 
Acidalium, 4800 from Syrtis Major, 5400 from Solis Lacus, and 8000 
from Sinus Sabaius. The name 'Propontis' signifies a lake or small sea 
preceding the great open sea ; since Propontis is in fact one of the largest 
lakes on the planet, and is the furthest away from the seas, the choice of 
name is not a happy one! 

HERCUL1S PONS (S, 1881-2). Broad isthmus, generally light grey, 
separating the two Propontides ; Schiaparelli saw it luminous yellow in 
188 1 -2, and this aspect persisted until 1886, when the isthmus appeared 
shaded. In 1903 Millochau showed it as interrupted in the middle, and I 
noted it as smoky (Fig 127). Danjon showed it cut off to the E in 1920. 
With the o m -83 on 28 January 1929 it appeared white. From Meudon, in 
March 1929, I observed it on a disk only 8"-2 in diameter. 

propontis D (S, 1 88 1 -2). This second important lake lies to the N of 
Propontis I, and is elongated in the same direction. Schiaparelli, who 
was the first to record it, detected it in 1881-2 and observed it until 
1886; in 1883-4 an ^ '886 the E part of it was the most sombre, while in 
the latter year it appeared very black and broader than Propontis I. The 
Italian astronomer saw it again, for the last time, at the end of his obser- 
vations in 1888, Cerulli represented it in 1898-9, and Millochau showed 
it as very extended and decidedly dark in 1903, when it was joined to 
Castorius Lacus. At this time I recorded it as oval, and just as important 
as Propontis I (Fig 127). G. Fournier drew it in 1913-4, and Phillips 
and Thomson showed it in 19 18. Danjon sketched it as oblong and 
sombre in 1920. Lyot and I saw it notching the northern snows on 
28 January 1 929, when it was very dark indigo blue. 

uiacria. The whole country between the Propontides, Euxinus Lacus 



261 



and Castorius Lacus is a half-tone, which extends a long way to the \, 
the NE and the N\Y. This shaded area, broadly triangular with a blunt 
angle to the S, was indicated by Beer and Maedler as early as 1837 and 
1839, and by Galle in 1839. Since 1858 it has been seen by Seech i. 
Kaiser, Cruls, Bceddicker, Trouvelot, Lohse, Molesworth, Phillips, 
Rheden, Ward, Buchanan, Ellison, G. Fournier, Quennisset and Dan- 
jon. I observed it from 1900 to 1905 (Fig 128), and also in 1913-4, 1924 
and 1929. 




Fig 128 The shaded land 0/ Diacria, 21 March hjoj. (0 m -2l6 reflector) 

Schiaparelli once wrote to me saying that he had seen Diacria white on 

10 December 1896. Secchi had drawn it as white, on the edge of the disk, 
in 1862. 

phlegra (S, 1881-2). Continental region. Originally the name in- 
cluded the area between the Trivium Charontis and the Erebus to the 

5, the Styx to the \V, the Boreas and Propontis I to the N, and the Titan 

11 to the E. However, I have brought it back to the E as far as the Hades 
I, so as not to include the very smoky region under the Trivium. This 
noticeable half-tone was represented by Galle in 1839 and by Beer and 
Maedler in 1839 and 184! ; subsequently it was shown by various obser- 
vers, including Secchi, Kaiser, Burton, Baeddicker, Schiaparelli, Terby 
and Danjon. I found it very intense from 1898 to 1905 (Fig 145); Lowell 
and Lampland photographed it in 1907. I saw it again in 191 1 and 191 5— 

6. Schiaparelli noted Phlegra as red, Bceddicker as greyish orange. 1 
found it shady red and slightly chestnut in 1929, 

Phlegra does not often whiten near the edge of the disk, but it was seen 



262 



to do so by Secchi in 1864, and also from Milan in 1888. 

azania. E segment of the original Phlegra, and less shaded than the 
rest of the region. This shading, analogous to that of Amazonis, is shown 
on drawings made in 1839 by Galle, and subsequently on those made by 
Bceddicker in 1881-2, and Trouvelot in 1883-4. ! also saw it, in 1900-1. 
The colour of Azania was chestnut-red as seen from Meudon in 1929, 
brighter than the colour of Phlegra. 

promontorium bon/e spei (S, 1 879). Cape of Phlegra, near Hecates 
Lacus. 

cebrenia (S, 188 1-2). Desert land, less smoky than Phlegra, lying 
under Elysium, where it is bounded to the S. It has the Anian to the W, 
the Gyndes and the Granicus to the H, and the Boreas to the SE. 
Cebrenia was observed as shaded by Beer and Maedler in 1832. The 
shading here was confirmed by many observers, including Galle, Secchi, 
Kaiser, Green, Burton, Bceddicker, Millochau and Danjon. I observed it 
from 1898 to 1903 and also in 191 1 ; Lowell and Lampland even managed 
to photograph it in 1907. 

Cebrenia very rarely whitens at the edge of the disk, but Secchi 
observed it to do so in 1864. 

stymphalils lacus (S, 1 888). Large dark shading on the Granicus, 
to the W of Propontis II. Schiaparelli made it smaller than Castorius 
Lacus in 1888, but could not see it at all in 1890. Molesworth in 1896-7, 
Cerulli, Phillips and Brown in 1898-9, Lowell in 1900-1, and Millochau 
and Lowell in 1903 all observed it. I saw it in 1900-1, as did G. Fournier 
in 1913-4, Bnault in 1918, and Danjon in 1920. Millochau showed it as 
pointed to the S. 

thymbr^s fons. Small lake on the Gyndes, seen from 1903 to 1905 by 
Lowell, who called it 'Thymbra'. 

mnemosyxes foxs. Another lake, to the W of Thymbrse Fons and 
lying on the same streak. Lowell noted it from 1903 to 1905, calling it 
'Mnemosyne*. 

sithonius lacus (S, 1 888). This is another lake, extended and dark, at 
the junction of the Gyndes and the Anian. Schiaparelli drew it in 188J-2, 
1888 and 1890. As observed from Milan, it measured io° in 1888 and 6° 
in 1890. It seems to be more important than Stymphalius Lacus. It was 



263 



also observed by Lowell, Douglass and Molesworth in j 900-1, Millo- 
chau, Gale and Lowell in 1903, Lowell in 1905, G. Fournier in 19 13-4, 
and Briault in 1918. Millochau showed it pointed to the S, like Stym- 
phalius Lacus, 

/etheria (S, 1881-2). Greyish region, enclosed between the Hephaes- 
tus to the S, the Adamas to the W, the Alcyonius to the N, and the 
Anian and the I iyblaeus to the E. The shading was first drawn by Galle 
in 1839. It was subsequently shown on drawings made by Secchi, Banks, 
Kaiser, Green, Schiaparelli, Boeddicker, Trouvelot and others, I often 
observed it between 1891 and 1903, and Lowell and Lampland photo- 
graphed it in 1907. Secchi found j^Ethcria red, mottled with more vivid 
specks. Boeddicker saw it as grey or orange- red ; Le Coultrc described it 
as pure rose. 

In 1909 Nangle observed a white patch on /Etheria. This land rarely 
whitens when seen obliquely, but was seen to do so by Webb and Brodie 
in 1856, Secchi in 1862, and Schiaparelli and Niesten in 1888. This 
whitening was recorded photographically by Quenisset in 1922. 

IRREGULAR STREAKS AND FINE DETAILS 

acheron (S, 1881-2). Vague diffuse streak, definite to the E and 
probably discontinuous, drawn by Schiaparelli between the Titan II and 
the Ceraunius. In 1839 Beer and Maedler indicated it as broad, but only 
in the E. In 1864 Dawes seems to have represented the Acheron as very 
broad, irregular and diffuse. In 1877 Flammarion showed only its E part. 
Schiaparelli observed it single in 1881 2, double in 1883-4, ant ^ single 
in 1886 and 1888. Millochau saw a broad, undulating streak here in 1903. 
Ward in 1905, Eddie in 1907, and Danjon in 1920 showed it — parti- 
cularly to the E — as broadened, billowy and pale. 

adamas (S, 1888). Vague nuclei lying between the Nodus Alcyonius 
and the Hephaestus, bordering a shading to the NE. Schiaparelli saw the 
Adamas double in 1888. Ten years later, I glimpsed it as diffuse and 
feeble; and in 1900-1 I could distinguish here only the boundary of a 
shading to the N. Millochau noted it as knotty and discontinuous, and 
interrupted near the Pactolus. 

264 









,/esacus (S, 1883-4). Band joining Hecates Lacus to Stymphalius 
Lacus. Schiaparelli glimpsed the Maaoaa as single in 1883-4, 1888 and 
1890. He also seems to have observed it in 1896. To me it seemed pale 
and diffuse between 1898 and 1901, as it also did to Millochau in the 
latter year. Millochau saw the .Esacus as interrupted. Denning showed 
it as linear in 1903, Danjon very broad in 1920. 

^ETHiops 1 (S, 1877). Cut-up streak following the meridian, and going 
from the Mare Cimmerium to the Hephaestus. In 1837 Beer and Mzedler 
showed two greyish masses here. In 1873 Green saw it only to the N. 
In 1877 Schiaparelli represented it as slightly convex to the VV, and 
sinuous; in 1879 it seemed to him to be conspicuous and rectilinear, with 
numerous minor sinuousities. This was a remarkable observation, in 
view of the fact that it was made with an o m -2i8 telescope. In 1881-2 
Boeddicker saw it only as the border of a shading to the E, but Schiapa- 
relli regarded it as well-defined, and he followed it until 1890. Holden 
drew it straight, Denning broad in 1888. I glimpsed it very vaguely 
between 1894 and 1901. From 1900 to 1903 Millochau was unable to 
follow it as far as the Marc Cimmerium, but he drew it as knotty to the X. 
In 1924 Bidault de 1'Isle drew it well to the S. In June I observed it as 
almost rectilinear; it was not broad, but was cut up and full of irregu- 
larities (Fig 8). In September I saw it disappear in the shading of 
.'Ethiopis. 

^ethiops 11. Straight line glimpsed by Schiaparelli in 1888, prolonging 
the iEthiops I as far as Sithonius Lacus. 

alcyonius (S, 1881-2). This was called Alcyonius Sinus in 1879. It 
is the border, to the SE, of the shading of Utopia. It appears on the 1841 
drawings made by Maedler. From 1856 to the present time Secchi, 
J. Phillips, Burton, Flammarion, Terby, Green, Schmidt, Bceddicker, 
Xiesten, Holden, Keeler, Millochau, Quenisset, Briault and others have 
always seen the Alcyonius as the border of the dark shading of Utopia. 
I confirmed this aspect between 1898 and 1903 (Fig 59), and in 1924. 
From 1 88 1 to 1890, however, Schiaparelli saw it in the form of a simple 
streak, sometimes black; he also drew it as black in 188 1-2. This de- 
scription certainly does not correspond to actuality! 

anian (S, 1881-2). Also called Fretum Anian. This broad, dark streak 
links Morpheos Lacus with Sithonius Lacus. The Anian was observed 

265 



as single from Milan until 1888, but double in 1890. Millochau repre- 
sented it as diffuse, and broken in the middle, in 1900-1. Danjon saw it 
as a confused shading in 1920. 

antveus (S, 1881-2). Irregular, knotty streak; the edge of a penumbra 
to the NE, which extends between the Laestrygon and the Cerberus. 
Boeddicker, in 1881-2, drew it only as the border of this grey area. 
Schiaparelli glimpsed it as double in 1883-4, but from Milan in 1888 
it appeared single. I saw it pale in 1896-7 and in 1907. Molesworth, in 
1900-1, noted it as the border of the shading; Denning drew it in its 
entirety in 1903. With the o m -83 I saw it excellently in 1909; it then 
ended in the middle of iEolis, without reaching the Cerberus, and form- 
ing a backward curve of shading to the NE. Its border was made up of 
three unequal nuclei — my Crucis, Antsei and Lupi Pontes. I confirmed 
this aspect in 191 1, 1924 (Fig 113) and 1926. 

arimanes (S, 1890). Line glimpsed by Schiaparelli between Gorgonum 
Sinus and the Eumenides. 

ascanius (S, 1881-2). Band noted by Schiaparelli, cutting Elcctris 
obliquely from Simeontis Sinus to Scamandri Sinus. The Ascanius was 
easy and dark from Milan in 188 1-2, appearing first broad and later very 
thin; the lower segment, left of Electris, was thus divided, and was the 
more shaded of the two. 

AVERNUS (S, 188 1-2). Sinuous, knotty streak, also making up the 
border of a shading to the NW, going from the Laestrygon to the Tar- 
tarus. Schiaparelli saw the Avernus double in 188 1-2, single in 1883-4, 
1888 and 1890; and he wrote to me saying that he found it difficult on 10 
December 1896. Hussey and Schseberle drew it broad in 1892, and Ward 
saw it in 1895. In 1909 and 191 1, from Meudon, I could distinguish only 
traces of it; but in 1924 I saw it as very beautiful and dark, convex 
toward the SE, making up the boundary of the half-tone mentioned 
above, and composed of two irregular nuclei — my Diana.- and Lyra? 
Fontes. It ended at Aquae Apollinares to the SE (Fig 113). This aspect 
was confirmed in 1926. 

boreas (S, 1 88 1-2). Knotty band, joining Propontis I to Hecates 
Lacus, and bounding the shading of Phlegra, Schiaparelli observed the 
Boreas in 1881-2 as a broad, black strait, and Bceddieker also saw it as 



266 



very dark. It was again seen from Milan from 1883 to 1886, and in 1888 
it was again broad, black and truly enormous. In 1890 it was very black; 
in 1896, dark and easy, as Schiaparejli told me in a letter. Ccrulli, Gale 
and Mee represented it in 1896-7, and Molesworth from 1896 to 1903. 
In the latter year, it appeared to me as the edge of the penumbra of 
Ccbrenia (Fig 127). Millochau made it knotty and rather feeble in 1903. 

CAMBYSES (S, 1890). Line glimpsed by Schiaparelli between the 
.-Ethiops and Cyllenius Lacus. 

cerberus i (S, 1881-2). This is a part of the Cyclops of 1877, and 
which often shows up as the most beautiful of the irregular streaks on 
Mars. It is very broad, cut-up, knotty and sombre, joining Trivium 
Charontis to the Pambotis Lacus, and forming the SE limit of the bright 
surface of Elysium. Bianchini did not see the Cerberus in 1779. It was 
recognizable on the 1783 sketches made by Hcrschel, who shows it as 
very evident, with a mean breadth of 10 degrees. Subsequently, Schrceter 
drew it as broadened and dark between 1785 and 1800; in the latter year 
it formed, in part, the prolongation of the vast dark surface of Cyclopia 
and of ^Ethiopis. It is clear that the Cerberus I was then extremely highly 
developed. Yet thirty to forty years later, Beer and Msedler did not draw 
it at all! However, on one occasion Galle showed it as broad and sombre 
in 1837, and he made it feebler in 1839; Secchi, in 1858, did not show it 
clearly. In 1862 it remained invisible; in 1864 Dawes showed it, and 
Lohse noted it as the demarcation between the brightness of Elysium and 
the upper penumbra, in 1873. Then, in 1877, only Schiaparelli observed 
it — and, moreover, only in December. The Cerberus was still very pale in 
1879, according to Burton and Schiaparelli. Yet in 188 1-2 Bceddieker 
indicated it as broad and dark; Schiaparelli saw it as doubled into two 
very black lines. Again double from Milan in 1883-4, * appeared at this 
time as broad and feeble to Trouvelot. In 1886 Schiaparelli and Denning 
noted it as pale; in 1888 Terby, Holden, Denning and Smart made it 
broad and intense, while Schiaparelli and Perrotin glimpsed it as double 
and sombre. It still appeared double in 1890, from Milan. Then, in 1892, 
Campbell, Keeler, Gale and Eddie noted it as broad and diffuse; Hussey 
and Stanley Williams made it double. I saw it pale in 1894, but very 
dark and momentarily double in 1896-7. Schiaparelli saw it as well- 



267 



marked, very broad and very sombre from 1898 to 1 901, when it was truly 
striking (Fig 1 24). Millochau saw it as knotty and blackish in 1 900-1, but 
less sharp in 1903, when to me it seemed decidedly pale, and almost 
reduced to nothing more than a border to the bright area of Elysium. 
Gale still made it feeble in 1905, but I saw it as more marked in 1907, 
when Lowell and Lampland succeeded in photographing it. In 1909 I 
noted it as very feeble, because of the general veiling; later in the 
opposition it was more clearly visible from Meudon, and seen to be 
made up chiefly of two irregular nuclei. With thco m -83, 1 confirmed this 
aspect in 191 1, when it appeared more intense (Fig 126). G. Fournier 
and Thomson saw it as very dark in 191 3-4, but I again found it feeble 
in 1 91 5-6. In 19 1 8 the Cerberus I appeared broadened and sombre to 
Mile Rcnaudot, Qucnisset, Thomson and Briault, and also to Danjon in 
1920. On 1 August 1924 Quenisset notified me of an enormous, extra- 
ordinarily intense development of the Cerberus I, which I was able to 
confirm in part on 2 August. With the o m -83, it then appeared broadened, 
very broken-up, and composed mainly of the two irregular nuclei men- 
tioned above; the whole system appeared blackish (Fig 122). This aspect 
was followed from Meudon until November, by which time the intensity 
of the streak had already diminished. It was pale and floccular in 1926. 
From 1896 to 1899 Ccrulli saw the Cerberus I as broken-up; Millochau 
noted two bridges over it in 1900-1, and another in 1903. The consti- 
tuent nuclei which I have observed, with their extremities, indicate three 
shaded breaks in the Cerberus I. In 1888 Terby often found the feature 
rose in colour; in 1918 Thomson saw it as greenish; in 1924 it seemed to 
mc to be very dark grey, almost blackish. 

The variations described above arc due partly to the interposition of 
vast yellow clouds; but there is no doubt whatsoever that the surface 
here sometimes darkens enormously, and that this darkening is not 
related to the seasonal cycle. 

cerberus 11 (S, 1881-2). Dubious prolongation of the Cerberus I up 
to the Mare Cimmerium. Baeddicker saw it only as the boundary of 
Cyclopia; to him in 188 1-2, it was smoky. From 1881 to 1884 Schia- 
parclli drew the Cerberus II as a straight line, and he did so again in 
1890, though he believed that it had shifted in position. It was again seen 



268 









from Milan in 1896: 'as an extremely delicate streak,' as Schiaparellt 
wrote to me at the time. I also suspected it. In 1898-9 Cerulli showed it 
as the border of the shading of /Ethiopis. I glimpsed it as vaguely double 
in 1 900-1; it was convex to the NW, and diffuse, in 1909 (Fig 8); and 
in 191 1 the visibility of Cerberi Fons seemed to me to contribute to the 
visibility of this optical line. 

In describing this region, I have found it convenient to divide the 
Cerberus into two parts. 

Cerberus in. Blackish band, narrow and sinuous, seen very distinctly 
by Millochau from 1900 to 1903, and which crosses the Mare Cim- 
merium between Cerberi Sinus and Hesperia. It is a prolongation of the 
Cerberus II (Fig 129). 




Fig 121) The streak of Cerberus ill, crossing the Mare Cimmerium in 
1 goo and 1903, according to Millochau. (o m S3 refractor) 

chaos (S, 1888). A streak which borders Elysium to the N, and marks 
the shaded boundary of Cebrenia. Galle observed it as broad and dark 
in 1837 and 1839, and Dawes indicated it as linear in 1864. Green and 
Lohse in 1873, and Schiaparclli in 1879, saw it as the border of the grey- 
ness mentioned above. In 1881-2 Bceddicker represented the Chaos as 
broad and diffuse, while from Milan it appeared extended and intense. 
Schiaparclli glimpsed it double in 1883-4, single between 1886 and 1890. 
I noted it as broad and diffuse from 1896 to 1899, when it marked the 
border of Elysium; I almost lost it in 1900-1, only to see it again as very 
pale in 1903. It was photographed by Lowell and Lampland in 1907; 
in 191 1, from Meudon, it appeared 5° broad, bordering the smoky 
Cebrenia (Fig 126). In 191 5-6 I saw it as very pale, and Danjon still 



269 



found it feeble in 1920. With the o m -83 in 1924 and 1926, I saw it as the 
border of the brightness of Elysium. 

COCYTUS (S, 1881-2). Band glimpsed by Schiaparelli in 1881-2, 
between the Sirenius II and Propontis L Denning drew it in 1903. 

Cyclops (S, 1877). Originally, this name was given to the streak which 
goes down as far as the Trivium Charontis, and only since 188 1-2 has it 
been restricted to the variable band which goes from Cyclopum Sinus to 
Pambotis Lac us. The Cyclops was invisible to Bianchini in 1719 (Fig 
130), but seemed extremely broad and sombre to Herschel in 1783; its 
width was then as much as 12 (Fig 131). It was drawn similarly by 





Fig 130 Bianchini (iyig), Fig 131 W. Herschel (1783) and Fig 132 

Schroter (1800) Great development 0/ the Cyclops and the Cerberus at 

the end 0/ the i8ih Century 



Schroeter in 1785, and later, in 1792, he showed it as very broad and very 
dark. From 1798 to 1800, when Cyclopia and a part of ./Ethiopia were 
dark, Schroeter drew here a vast triangular gulf, comparable with the 
Syrtis Major (Fig 132); this was confirmed by van de Sande Backhuy- 
zen. 7 According to Schrceter's drawings, it seems that this vast mouth 
had diminished in 1802. 'Thirty years later, no trace of it remained, the 
Cyclops itself then being invisible to Beer and Maedler. Then, in 1837, 
Galle drew it as broad and dark. In 1858 Seech i showed a vast, though 
feeble, shaded area on Cyclopia, which coufd only correspond to a new 
though less important development of the Cyclops. Nobody drew it 
clearly in 1862, but Dawes showed it in 1864. According to Schiaparelli, 
Gledhill observed it in 1871; Lohse represented it as normal in 1873. 
It was pale as seen by Green and Schiaparelli in 1877, when from Milan 



270 



its inclination to the meridian was estimated as 20 . The Italian astrono- 
mer followed the Cyclops in 1878 until the disk of Mars had been re- 
duced to 5". In 1 879 it was feeble to Burton, but seemed very easy from 
Milan. In 1881-2 Bceddicker saw it as complex and dark; Schiaparelli 
made it double. He wrote: 'The gemination of the Cyclops in 1882 has 
been a remarkable case; it is so strong and so marked that no other object 
upon the disk can be compared with it.' 8 He also spoke of 'these two 
branches of the Cyclopes' which 'are separated, and are splendidly 
visible' ; he judged them to be 'completely black', and 'so uniform in 
breadth and colour that one cannot avoid considering them as artificial 
traces' 9 (Fig 7). At this time Schiaparelli saw the Cyclops bordered by a 
white patch. 1 " In 1883-4 there was the same doubling as seen from 
Milan, with an oblique central line as at the previous opposition; but the 
Cyclops was then less dark, and Bceddickcr even drew it as very feeble. 
Schiaparelli drew it single, straight and black in 1886, sombre in 1888, 
double and blackish in 1890; Giovannozzi glimpsed it with an o'"-io8 
telescope. Schseberle and Keeler in 1892 and Campbell in 1894 made it 
fairly intense. To me it seemed feeble and diffuse in 1894; optically 
double in 1896—7, at the time w : hen Schiaparelli wrote to me saying that 
he had found it sombre and lying along the meridian. Subsequently I 
saw it as intense in 1898-9 and pale from 1900 to 1903 ; I was unable to 
see it in 1905, but I noted it as reasonably marked in 1907. I saw it with 
certainty in 1909, with the o m -2i6 reflector; from Meudon it appeared 
feeble, irregular and discontinuous. I still found it pale in 1911, but I 
could not see it between 1913 and 1916, and Danjon drew it diffuse in 
1920. Then, in 1924, Bidault de TIsle showed it well on 9 September. 
With the o m -83, also in 1924, I could hardly see it except at the begin- 
ning of the year; its site was occupied by a yellow area which later turned 
to bright rose (Fig 3). It was easy, but diffuse, in 1926. With the great 
refractor I saw it well in 1927, with a magnification of 1250 on a disk 
7"-8 in diameter. 

dry as. Curvilinear streak on Pharthontis, convex to the SW, and 
bordering a stronger shading above. 1 observed it from Meudon in 1909 

(F'g 133)- 

ekebus (S, 1879). Indefinite band and alignment of lakes between the 



271 



Trivium Charontis and the Acheron. It makes up the border of the 
shading to the NW. Dawes showed traces of it in 1864. Schiaparelli 
observed the Erebus as diffuse in 1879, double from 1881 to 1884 and in 
1888 but single in 1886 and 1890. He described it to me as difficult in 
December 1896. Hussey drew it as linear in 1892, and Campbell glimpsed 
it in 1894. 1 observed it diffuse and pale in 1896-7, and as the border of 
the greyness of Azania in 1900-1. Denning drew it as linear in 1903; 
Millochau, more accurately, as broad and sinuous. The Erebus appeared 
broadened and pale to Danjon in 1920, and to me in 1929, when its 
colour was chestnut-reddish-vermilion. 

The lakes of Ascania Palus, Aphnitis Fons and Hypefeei Fons con- 
tribute to the elusive visibility of the Erebus. 

erinnys (S, 1881-2). Straight line, glimpsed by Schiaparelli in 1 881-2, 
between Sirenum Sinus and Titanum Sinus. It was also drawn by 
Hussey ten years later. 

eumenides (S, 1881-2). This is the Oceanus Fluvius of 1877, going 
from Phoenicia Laeus to the Titan. It is really the knotty border of the 
shading of Amazonis. Secchi and Kaiser in 1 862, and Trouvelot, Green, 
Terby, Niesten and Lohse in 1877 saw it simply as the S limit of the 
lower greyness. Schiaparelli noted it as broad in 1877. '* was tnc same to 
Burton in 1879, when from Milan it was seen only to the E. It appeared 
double to the Italian astronomer in 188 1-2, linear from 1883 to 1888, 
double again in 1890. In 1892 Hussey, Campbell and Schseberle dis- 
tinguished it only at its E end, as did Campbell and Schseberle in 1894, 
when I glimpsed it as decidedly diffuse. Flammarion caught sight of it 
in 1896. From 1898 to 1901 it seemed to be broad and floccular. My 
observations in 1909 with the o m -z 16 reflector showed me the Eumenides 
as the boundary of the penumbra to the N, an aspect which was con- 
firmed photographically. With the o m '83, I always saw it like this until 
1929, and it was also observed by Danjon in 1920. Schiaparelli saw the 
Eumenides 'fox-yellow' in 1883-4, re d m 1886. I noted it as chestnut 
vermilion in 1929. 

eunostos l (S, 1877). Broad streak, bounding the brightness of Elysium 
to the SW. The Eunostos I was first shown by Galle in 1837, and Dawes 
certainly drew it before 1867. It was pale to Lohse in 1873, vei 7 feeble 






to Green and Schiaparelli in 1877, diffuse to Burton and Schiaparelli in 
1879. Bred dicker showed it as broad and floccular in 1881-2, when it was 
seen double from Milan — as it was also in 1883-4. Schseberle in 1892 
and Campbell in 1894 noted it as diffuse. I was unable to find it in 1894, 
but from 1896 to 1901 I observed it as nebulous, and as the reinforced 
demarcation between the brightness of Elysium and the adjacent shad- 
ing. Lowell and Lampland photographed it in 1907 as the boundary of 
the whitish area of Elysium. With the o m -83 in 1909, 191 1, 1924 (Figs 8 
and 126) I saw it as a little broader than it appeared with instruments 
of medium aperture. I saw the streak well in 1927 with the o m -83, 
using a magnification of 1250 on a disk of Mars reduced to 7"-8. In 1886 
Terby described Eunostos I as being of a rose tint. 

eunostos 11. Diffuse prolongation of the Eunostos I as far as Nodus 
Alcyonius. According to Schiaparelli, Eunostos II was seen by von 
Franzenau in 1864 and by Green in 1873. From Milan in 1877 it 
appeared very black, and convex to the NE; it was single from 1883 to 
1886, and double in 1890. I saw it as a border of the shading to the left, 
from 1898 to 1901. Wih the o m -83, it was diffuse in 1927. 

For convenience, I have divided the Eunostos into two parts, 

EUROTAS (S, 1888). Irregular streak, going from Maeotis Palus to 
Castorius Lacus, and bordering the greyness to the N. In 1888 Terby 
represented it as broad but feeble. In this year Schiaparelli described it 
as single, but to him it seemed double in 1890, with its branches con- 
verging to the W. Between 1898 and 1903 I saw it simply as the demarca- 
tion of the shading (Fig 128). Molesworth drew it from 1898 to 1903. 
Eddie described it as pale in 1907; in 1918, Briault distinguished it only 
as the border of the shading to the NW. Danjon drew it as intense in 
1920. 

fevos (S, 1888). Band probably joining Castorius Lacus to Propontis I, 
and bordering the shading to the K. Schiaparelli described the Fevos as 
single in 1888, double in 1890; Molesworth drew it from 1898 to 1903. 
In 1903 it appeared to me only as the border of the greyness of Diacria. 
In 1907 Eddie estimated its breadth as 5 . 

galaxias (S, 188 1-2). 'Extremely fine' line glimpsed by Schiaparelli 
in 1 88 1-2, cutting Elysium from S to N. Molesworth saw it as double in 



272 



273 



1896-7. I observed it only as a feeble penumbra in 1 900-1, 

GlGAS (S, 1877). Diffuse shading, vague and decidedly discontinuous, 
glimpsed by Schiapareili as one or two lines of the arc of a small circle 
joining Lucas Ascraeus to Giganturn Sinus. Maedler showed traces of it 
to the SW in 1837, and in 1864 Dawes saw a part of it in the form of 
broad, shaded-off complexes. In 1877 Trouvelot observed the E part of 
the Gigas as a border of the shading to the N, while at this time 
Schiapareili saw it broadened toward the NE. In 1879 Burton, and in 
1 881-2 Bceddicker, suspected it only as a half-tone to the SW. Schia- 
pareili saw it doubled all along its length in 1882, and followed its 
gemination on a 9" disk. He again saw it double in 1883-4, when 
Trouvelot could distinguish it only as an ill-defined shading to the SW, 
and Lohse another to the NE. From Milan, the Gigas appeared single 
from 1 886 to 1888, double again in 1890. In 1894 Hussey saw only its 
SW part, Campbell the NE. I glimpsed it in the SW from 1894 to 1897, 
and in 1898-9 Rheden showed it at first broad, then double. In 1905 
Ward could follow it only as far as Giganturn Sinus, and in 1907 
Crouzel saw its E part as a border of the penumbra to the N. In 1909, 
with the o n, -2i6 reflector, I saw it only to the SW; it appeared sinuous — 
yet with the o nu 83 I could see no trace of it. In T929 I saw its E extre- 
mity, Schiapareili saw the Gigas yellow-brown in 1882, reddish in 1883- 
4, brick-red in 1886, and again reddish in 1890. It was red chestnut to 
the E, in 1929. 

It is thought that the image of the Gigas is formed by the optical 
joining-up of Jovis Lacus, Biblis Fons, Nodus Gordii, Phrygius Lacus, 
Medusae Fons and the SSE border of the shaded-off area of Mesogaea. 
GORGON (S, 1879). Very irregular streak, emanating from Gorgonum 
Sinus and losing itself by spreading out to the N. In 1879 Schiapareili 
described the Gorgon as fine and black to the S, but broadened or 
shaded-off toward the Oceanus Fluvius or the Eumenidcs. This is an 
excellent description of it. In 1881-2 Schiapareili drew the Gorgon as 
very thin and rectilinear. It was still linear as seen from Milan in 1883-4 
and 1888, and was again broadened toward the N in 1890. Hussey drew 
it as narrow, Schaebcrle broad in 1892. Campbell drew it in 1894; I 
glimpsed it in the same year, and also in 1898-9. With perfect images in 

274 







1909, using the o'"'83, I saw here a vast shaded area, tapering and 
sinuous to the S, but greatly broadened and curved back toward the 
NNW. I confirmed this aspect from Meudon in 1911, 1924 (Fig 111) 
and 1926. In 1909 the colour of the Gorgon seemed to me to be very pale 
green (e = 8°). 

GRANicus (S, 1888). Band bordering the shading of Diacria to the W. 
Bceddicker observed the Granicus in this form in 188 1-2. Schiapareili, 
Denning and Perrotin observed it in 1888, but Holden showed it only 
as the boundary of the greyness below. It was seen double from Milan in 
1890, 1 glimpsed it from 1900 to 1903. 

grl'S. Short streak, convex to the N, joining Cyclopum Sinus to 
Cerberi Sinus. Schaebcrle was the first to draw it, in 1892; Millochau 
saw it from 1900 to 1903. With the o m -83, Idrac and G. Fournier noted 
it in 1929, and Baldet and I observed it in 1924 (Fig. 1 13). 

GYNDES (S, 1886). Broad, knotty streak, making up the border of the 
shading of Panchaia, between Stymphalius Lacus and Sithonius Lacus. 
The Gyndcs is shown as a broad, diffuse band on a sketch made in 1856 
by de La Rue. Burton showed it as very broadened and very intense in 
1 87 1 ; so did Lhosc in 1873. Schiapareili saw it broad and dark in 188 1-2, 
diffuse in 1886, double and intense in 1888 and 1890. In 1888 Holden 
saw it only as the border of the greyness to the N, though Niesten de- 
scribed it as sombre. Schiapareili described it to me as easy in 1896, and 
1 distinguished it quite well in 1900-1 ; sometimes it appeared as smoky. 
In this year, and also in 1903, Millochau saw it only as the border of the 
shading below (Fig 147). Molesworth and Phillips saw it double in 1903, 
and Phillips also in 1905; in 191 5-16 Briault saw it only as the border of 
the shading. This was also his description of it in 1918. Quenisset showed 
it as blackish in 1920; Danjon, broadened and diffuse. 

hades 1 (S, 188 1-2). Band going fromTrivium Charontis to Propontis, 
making up the E boundary of the greyness of Phlegra. Dawes drew a 
trail here in 1864; Schiapareili observed the Hades as broad and black in 
1 88 1-2, reasonably sombre in 1890. In 1883-4 Lohse could distinguish 
it only as the border of the shading to the right ; Hussey drew it as linear 
in 1892. From 1898 to 1903 (Fig 145) and in 19 15-6 I observed the 
Hades 1 as the intensified and smoky boundary of the half-tone of 

275 



Phlegra. With the o m -83, I again saw it in this form in 1929, when the 
band appeared reddish chestnut. 

hades 11. Prolongation of Hades I from the Propontides up to Arsenius 
Lacus. Schiaparelli glimpsed this band in 1883-4, and reobserved it in 
1888 and 1890. 

For the sake of clarity. I have divided the Hades into two parts. 

heph^estus (S, 1 88 1 -2). Shaded-off feature adjoining Elysium to the 
W. Kaiser indicated it in 1864 as very extended and intense, and Dawes 
drew it before 1867. In 1873 Schmidt showed it clearly. Schiaparelli 
described it as nebulous in 1879, double and intense from 188 1 to 1884, 
vast and floccular in 1886, dark and double in 1888, and quadruple in 
1890. At this time he called it 'a gemination of geminations'. 11 Yet in 
1883-4, Lohse saw here only a broad shading. In 1888 Neisten repre- 
sented it as decidedly dark; Terby, Holden and Denning as pale and 
nebulous. I glimpsed it as extremely feeble and doubtful from 1894 to 
1897, and as an irregular dark shading in 1903, though Millochau could 
not distinguish it. With the o m -83 I could see nothing of it in 1909 or 
191 1 ; but in 1924 1 saw a triangular greyish patch, decidedly sombre (Fig 
8) adjoining the rosy triangular shading of iEthiopis. The same aspect 
persisted in 1926-7. The colour of the Hephaestus appeared dark red to 
Schiaparelli in 188 1-2, vivid red in 1888. 

herculis column/e (S, 1 877). Broad band, sometimes dark and 
variable, marking the temporary limit of the greyness of Icaria, joining 
the 'beak' of the Mare Sirenum to the Aonius Sinus. Secehi and Kaiser 
showed it broad and dark in 1864. Subsequently Schiaparelli and the 
Henry brothers observed Herculis Columnae as intense, Green as pale. 
From Milan it then seemed 'one of the most easily visible of the canals' 
on a disk of Mars reduced to 5*-2. 12 The aspect was the same to Schia- 
parelli in 1879, when the Herculis Columnae bordered the shading to the 
SW. The Italian astronomer saw it again in 1881-2 and 1890. In 1892 
Stanley Williams drew it as sombre, while Schiaparelli described it as 
dark; but at this time Schaeberle, Keelcr, and myself with the o ,u -io8 
telescope saw no trace of it, so that the shading of Icaria ended at the site 
of the Hyscus (Fig 108). Barnard, Campbell and Schaeberle saw it in the 
same form in 1894; but in this year, as in 1896-7, I was able to suspect 



276 



its existence. With the o m -83 1 saw nothing of it in 1909 or 191 1 ; the 
region was drowned in the shading of Icaria, which extended as far as 
the Hyscus. However, in 1924 the greyness did not extend as far as the 
site of Herculis Columns (Fig 80). I could clearly see the true Herculis 
Columnae as a broad, diffuse band from Meudon in 1926. To Schia- 
parelli, in 1879, me c °l° ur of tne strait seemed to be azure-grey. 

HESPERUS. Intense shading, separating Eridania from Hesperia. 
Maedler indicated it in 1832; subsequently it was shown by Schmidt in 
1862, Green in 1873, and by Schiaparelli from 1877 to 1890, who noted 
it as broad and sombre and diffused on to Hesperia. I observed it as 
floccular from 189410 1903; from Meudon, from 1909 to 191 1 and 1924 
(Fig 113) it was better defined. In 1909 Hale photographed it as the 
border of the shading near the island of Hesperia. 

hybueus (S, 1881-2). Greyish boundary of Elysium, between the 
Hephaestus and Morphcos Lacus. It is slightly convex to the NW; to 
the SE it marks the border of the shading of /Etheria. The Hyblaeus was 
first indicated by Galle in 1837; it was then broad and dark. Secehi drew 
it in 1858, Dawes before 1867, and Green and Lohse in 1873, showing 
it broad and diffuse. Later, in 1879, Schiaparelli saw it simply as the 
shaded boundary of .-Etheria, Bceddicker showed it floccular in 1881-2; 
in this year Schiaparelli saw it double, as he also did in 1883-4. Between 
1886 and 1890 it was shown as diffuse from Milan. I was unable to dis- 
tinguish it in 1894, but I saw it reasonably easily from 1896 to 1903, 
often as the border of the greyness to the W. From 1900 to 1903 
Millochau noted it as pale and billowy. From Meudon, from 1909 to 
1 926, 1 always saw it as the broad, strengthened border of the half-tone 
of /Etheria (Fig 126). In 1927, with X 1250 on a 7"-8 disk, I was able to 
see it. Terby found the Hyblaeus rose-coloured in 1888. 

UESTRYGON (S, 1877). Beautiful filamentary streak, discontinuous and 
knotty. Disregarding various undulations, it goes in almost a straight 
line from Laestrygonum Sinus to Trivium Charontis. Secehi showed the 
Lsestrygon as early as 1858, and Schiaparelli has commented that in 1865 
Kaiser saw it as the border of the greyness to the W. In 1878 the Italian 
astronomer could see it on a disk of Mars only 6"' 5 in diameter. In 1879 
it appeared to him to be easier, convex to the E and broadened to the N ; 



277 



in 1 881-2 it was single, but double again in 1888 and 1890. Trouvelot 
showed it as feeble and diffuse in 1883-4. Hussey observed it in 1892, 
and Campbell described it as linear in 1894. I glimpsed it feebly in the 
latter year, and I saw it as a black line, for an eighth of a second, in 1896 
on a 6*7 disk. Flammarion also saw it at this time. Schiaparelli wrote to 
me saying that in December 1896 he had seen it as narrower than the 
Cyclops. To me it appeared diffuse in 1898-9 and in 1907. With the 
o m -83 in 1909 I was able to see it as a series of filaments and small lakes, 
full of irregularities and decidedly rectilinear, sometimes undulating. I 
confirmed this from Meudon in 191 1, 1924 (Fig 8) and 1926. 

lethe (S, 1877). Group of very feeble and ill-defined shadings, going 
from Syrtis Minor to the Hephaestus. In 1877 Schiaparelli described the 
Lethe as one of the most difficult objects he had encountered on Mars. 
In 1879 ^ e saw 't as almost rectilinear and always broad and sombre, 
with numerous very small sinuosities along its course; at this time Burton 
showed it as very feeble. In 1 881-2 Bceddicker represented it as a border 
of the shading to the NW. Niesten made it narrow to the S, broad to the 
NE; Burton, merely narrow; and Schiaparelli linear, an aspect which he 
continued to note up to 1890. I glimpsed it very vaguely in 1894 and 
in 1898-9, but from Meudon I could not even suspect it. 

The point of Syrtis Minor together with the presence of Cyllenius 
Lacus and several other shadings is sufficient to produce the illusion of 
the line of the Lethe. 

LYCUS (S, 1888). Amorphous shading, glimpsed by Schiaparelli in 
1888 as a line joining Phcenicis Lacus to Castorius Lacus. It was con- 
firmed by Cerulli in 1896-7. 

lyncteus (S, 1890). Line glimpsed from Milan between the Hephaes- 
tus and Tritonis Lacus. 

Minos (S, 1890). Branch of the Laestrygon, going to the W of Trivrum 
Charontis. In 1883-4 Bceddicker drew a shading here, which Schia- 
parelli glimpsed as linear in 1890. 

orcus (S, 1881-2). This is the W part of the original Oceanus Kluvius, 
and a border of the shaded area toward Amazonis. Beer and Maedler 
indicated traces of it in 1832. In 1877 Green saw it only as the demarca- 
tion line of the northern greyness, while Flammarion and Schiaparelli 



278 



described the Orcus as broad and nebulous. In 1879 Burton called it the 
border of the penumbra to the N, while Schiaparelli recorded only 
traces of the band. Subsequently, in 1882, the Orcus was seen double 
from Milan; it appeared linear from 1883 to 1886, and again double in 
1888 and 1890. Schiaparelli wrote to me that he had found it broad, very 
pale and shaded on 10 December 1896. Kccler saw a streak here in 1892. 

I was able to glimpse it as reasonably broad and pale from 1894 to 1901 ; 
Flammarion noted it as diffuse in 1896. Denning traced a black line here 
in 1903. I again glimpsed it from Juvisy in 1909, with the o m -2i6 re- 
flector, as the border of the half-tone to the N, and I saw it vaguely from 
Meudon in 191 1 and 1924; it was better observed in 1929, when its 
colour was smoky reddish-vermilion. 

pactolus (S, 1888). Diffuse band, knotty and irregular, running in a 
curve, convex to the SW, from Pambotis Lacus to the Hephaestus. It is 
also the border of the half-tone to the N. It was in this form that the 
Pactolus was observed by Bceddicker in 188 1-2, but Schiaparelli drew it 
double in 1888. I glimpsed it as diffuse in 1896-7. From 1900 to 1903 
Millochau, using the o m -83, saw it as irregularly knotty, discontinuous, 
sinuous and convex to the SW. 

phlegethon (S, 1 879). Vague shading; a continuation of the Hy- 
draotes-Nilus, from Mareotis Lacus to Propontis I. Galle showed a 
nebulous streak here in 1839; Flammarion showed only the E part of it in 
1877, anc * Schiaparelli saw it, though not clearly, in 1879. From Milan 
the Phlegethon appeared fine from 1881 to 1882, diffuse in 1886 and 
1890. I glimpsed it as broad and nebulous between 1896 and 1903. 
Millochau saw only its W part in the latter year, as a broad, irregular 
shading. I reobscrved it in 1903, and Danjon indicated it as floccular to 
the W, but clearer and broader to the E, in 1 920. 

plutus (S, 1888). Confused band, apparently running from the Titan 

II to Hecates Lacus; it was noted as pale by Schiaparelli between 1888 
and 1890. The existence of a condensation on the Hades I, and those of 
Hypelaei Fons and Titanum Fons, seem to contribute to the visibility of 
the Plutus. 

pyriphlegethon (S, 1 88 1 -2). Irregular streak, broad and discon- 
tinuous, going from Phcenicis Lacus to Propontis 1. This is the pro- 



279 



longatEon of the Eosphoros of 1877. Secchi represented the Pyriphle- 
gcthon to the NW in 1864, and Trouvelot observed traces of it to the S 
in 1877. In this year Schiaparelli saw it shaded, and in 1878 he followed 
it until the disk of Mars had been reduced to 5*-2. In 1879 it was seen 
from Milan only in its S part. In 188 1-2 Schiaparelli saw it double; in 
1883-4 ne found it irregular; in 1886, diffuse; and he again saw it double, 
sometimes only to the NW, in 1890. Husscy observed it to the S, in 1892. 
I glimpsed it as floccular and broad, especially to the NW, from 1894 to 
1897, and also in 1903. From Meudon, I could see it only to the NW in 
1909 and 191 1 ; in 1924 I noted it to the SE, and found that it appeared 
broadened to the NW. I again saw this NT part in 1929. Schiaparelli 
found the Pyriphlegethon reddish in 188 1-2; I found it red chestnut in 
1929 (e = iii°). In 1898-9 Cerulli described it as 'a chain of aligned 
shadings*, 13 and the existence of Biblis Pons, Bandusiae Pons, Feren- 
tinas Lacus and Ascania Palus shows that this comment is justifiable. 

rhyndacus. Nebulous streak, which I saw in 1 900-1, together with 
Millochau and Kibbler, emerging from Propontis I and going toward 
the NNW. Millochau found it discontinuous. 

scamander (S, 1 877). Rather light shading, very broad and very 
diffuse, separating Electris from Eridania. In 1877 Schiaparelli found the 
Scamander easier than the Simois, and recognisable on a 9" disk; it was 
plain more because of its breadth than its darkness, and it was poorly 
defined. In 1879 he observed it without difficulty; at first it was smoky, 
and then changed into a fine line, inclined to the meridian by 20 to the 
SSW. In 1 88 1 -2 he saw the Scamander as very considerably broadened. 
Schseberle in 1892 and Campbell in 1894 showed it as excessively broad. 
In 1909, with the o m -83, I saw it concave to the W, and as the border of 
the then rosy and luminous Eridania. In 191 1, 1924 and 1936 it appeared 
to be as very broad, nebulous, and very feeble as seen from Meudon. 

simois (S, 1877). Magnificent irregular streak, sometimes sombre, 
curvilinear and decidedly convex to the E, going from Atlantis I to the 
Marc Chronium. It separates Phasthontis from Electris, and broadens 
into a funnel to the S. Schiaparelli observed the Simois as difficult in 
1877; it was curved back, as it also was in 1879, when to him it appeared 
broad and very dark: 'One of the most evident canals on Mars', 14 con- 



280 



tained in a broader shading which enveloped it on both sides. In 1881-2 
he saw it black, as broad as the Nilosyrtls. In 1903 Moles worth noted it 
chiefly as bordering a stronger shading to the left. In 1909, from Meu- 
don, I saw it as superb ; with the great refractor it was convex to the E, 
sombre, and widening into a gigantic trumpet toward the S (Fig 133). 
Ill-defined in 191 1 , it seemed to me very much broadened, irregular, and 
pale in 1924 and 1926. The Simois darkens when seen near the limb of 
Mars. 







Fig 133 The Simois, very clear though seen obliquely, on 6 October 1900. 

(o m -8j refractor) 

S1RENIUS I (S, 1877). Schiaparelli gave this name to the long, irregular 
streak which runs from Sirenum Sinus to Palus Masotis. To me it seems 
convenient to divide it in two ; thus my Sirenius I stops at the Nodus 
Gordii to the N. This Sirenius I can be recognised on a drawing made in 
1862 by Banks; and in 1864 Secchi showed it as marked, while Dawes 
made it broad and double. In 1877 Schiaparelli saw it broadened into a 
trumpet to the N, following it until the disk of Mars was reduced to 8"- 2. 
In 1879 he described it as paler, and again broadened below; but this 
broadening seemed to him to be due to a tributary corning in from the 
NNW, In 1 881-2 he saw it as double, and in 1886 ana 1890 as single. 
Hussey, Schaiberle, H. C. Wilson and Keeler in 1892, and Campbell in 
1894, showed it in the same form. To me it appeared very broad and 
diffuse from 1894 to 1897, and Eddie saw it as wavy in 1907- With the 
o m -83, in 1909, I saw it narrow and sinuous to the S, and broadened to 
the N in a vast pale, irregular shading. I confirmed this aspect from 



281 



Meudon in 191 1, 1924 (Fig. 113) and 1926. In 1909 the Sirenius I 
seemed to mc to be a very washed-out green. 

sirenius u. This is the N segment of the Sirenius, running from 
Nodus Gordii to the Maeotis Palus. It, also, is shown as broad and diffuse 
on the drawings made by Banks in 1862 and Dawes in 1864, Burton 
showed it as very nebulous in 1879. Schiaparelli recorded it as double in 
1881-2, but then observed it as single until 1888, although in 1886 he 
noted it as broad in the middle and full of small irregularities. I glimpsed 
it as broad and diffuse in 1894; Eddie in 1907 made it very extended to- 
ward the Eurotas. Danjon showed it as shaded and very broad in 1920, 
and I sometimes saw it equally plainly in 1924. Schiaparelli described the 
Sirenius II as reddish in 1886. 

styx (S, 188 1-2). This is the Palus Stygia of 1879. It is a broad, dark, 
knotty streak going from the Trivium Charontis to Hecates Lacus. It 
thus forms a demarcation between the strong greyness of Phlegra and 
the brightness of Elysium. The Styx was described as broad and sombre 
by Galle from 1837 to 1839; Beer and Masdler showed it on their chart 
in 1838. Dawes saw it in 1864; Green made it broad and intense in 1873, 
while to Lohse it seemed to be the shaded border of Elysium. In 1879 
Schiaparelli saw it broadened toward the NW; Burton distinguished it 
only as the border of the shading preceding it. In 1881-2 Schiaparelli and 
Boeddicker again observed it as broad, sometimes blackish. Trouvelot 
and Lohse adjudged it broad and diffuse in 1883-4, while to Schiaparelli 
it seemed double — though thereafter, until 1890, he saw it as single. The 
Styx was again observed as decidedly dark and broad by Holden, 
Terby, Smart and Denning in 1888 and by Schiaparelli in 1892; in the 
latter year Keeler saw it interrupted by a bright streak. In 1894 I could 
not see it at all, but in 1896-7 it was intense, Schiaparelli writing to me 
that he noted it as 'very considerable'. From 1898 to 1901 I found it 
decidedly sombre, but in 1903 it appeared both to me and to Millochau. 
Lowell and Lampland photographed it in 1907 as bordering the*white- 
ness of Elysium. From Meudon, it appeared to me to be veiled in 1909, 
but in 191 1 (Fig 126), 1924 and 1926 I observed here a broad, dark band, 
strengthening the shading of Phlegra. Mile Renaudot in 1915-6, and 
Danjon in 1920, again noted it broadened and sombre. Molesworth saw 



282 









the Styx as knotty in 1903, and Terby noted it as rose-tinted in 1888. 

tantalus (S, 1 888). Modified course of the Phlegethin, flowing into 
Castorius Lacus and not into Propontis I. It was observed by Schia- 
parelli in 1888; Danjon showed it as a diffuse penumbra in 1920. 

Tartarus (S, 1 88 1-2). Very broken-up border of the shading of 
Mesogasa, running in a sinuous curve from the NE front of the Mare 
Sirenum to Trivium Charontis. Msedler drew the Tartarus in 1832 and 
1839 as a vast, irregular shading. Cruls glimpsed it as an ill-defined 
penumbra in 1877, Lohse as the border of a broad band mixing in with 
the Titan. In 1879 Niesten saw it only as the border of the shading of 
Mesogsea, and Burton sketched here a grey area broadened toward the 
NW; Schiaparelli saw the Tartarus as black and narrow to the S, 
broadened and smoky to the NW. From Milan it was subsequently 
observed as linear and reasonably intense until 1890. Trouvelot showed 
it as diffuse in 1883-4, while Schaeberle made it more linear in 1892. I 
glimpsed it feebly from 1894 to 1899. Then, with the o m -8^ at Meudon in 
1909, I saw it easily as the excessively irregular, broken-up and undu- 
lating W boundary of Mesogaa. With the o m -83 I confirmed this aspect 
in 191 1, 1924 (Fig 8) and 1926. I made it greenish-greyish in 1909 (e = 
35 ) and 1924 (e = 40 ), but this broad streak was a striking brown- 
reddish-vermilion in 1929 (e = 107°). Cerulli noted in 1896-7 that the 
'I artarus darkens when seen near the limb. 

THERMODON (S, 1 879). Genuine band seen on Phaethontis, between 
Palinuri Sinus and the Mare Sirenum. It was recorded by Schiaparelli 
in 1879, when it was pale and difficult. This was an observation to be 
admired. I confirmed it unmistakably from Meudon in 1924; the 
Thermodon then appeared as a narrow irregular thread, streaked in the 
manner of classical lightning, and excessively feeble. 

titan 1 (S, 1877). The name Titan was given by Schiaparelli to the 
band running down the meridian from Titanum Sinus to Propontis I 
and beyond. For convenience I have divided it into two parts, with my 
Titan I going from the Mare Sirenum to the Orcus. There is no band 
here, but only the broad, complex shading of Mcsogaea. Lohse observed 
the Titan I as very broad in 1877; it was also very dark. Schiaparelli saw 
it broadened toward the N, and followed it in 1878 until the disk of Mars 



283 






was reduced to 5"' 2. Lohse rcobserved it in 1879, w ' tn Niealen; Schia- 
parelli saw it as fine and obscure to the S, broad and nebulous to the N. 
Uurton confirmed the broadening to the N. In 1881-2 Bceddicker repre- 
sented the Titan I as broadened and diffuse, Schiaparelli as double. From 
Milan it then appeared single until 1886, double in 1888, single again in 
1890. Holderi drew it as reasonably large in 1888, Hussey, Keeler, 
Schaeberle, Niestcn, and Stuyvaert in 1892, and Campbell in 1894, drew 
it as fairly narrow. In 1894 1 sometimes glimpsed it; in 1896-7 I sus- 
pected that it might be double; in 1 900-1 I recorded it as broad and 
nebulous. Denning saw it linear in 1903, which is an illusion. I glimpsed 
it vaguely in 1907. With the o m -83 in 1909, 1911, 1924, 1926 and 1929 I 
saw that the Titan 1 does not exist; the illusory line is produced by the 
shaded mass of Mesogsca, enhanced by the point of Titanum Sinus and 
the lakes to the N (Fig 113). Cerulli described the Titan I as granular 
in 1896-7, and even stated that he had found it most conspicuous when 
seen obliquely. Schiaparelli found it grey, not red, in 1882. 

titan 11. N part of the Titan, going from the Orcus to the Propon- 
tides, and lined up with the spaccd-out lakes. It was recorded as double 
by Schiaparelli in 1881 2, and then single until 1886; double in 1888; 
single in 1890. I glimpsed it as broad and double in 1896-7, and very 
broad and nebulous in 1900-1. Cerulli noted it as single in 1896-7, 
double in 1898-9. Denning drew it as linear in 1903. 

vultur (S, 1890). Line glimpsed by Schiaparelli on .Ethiopis. 

xanthus (S, 1877). Broad band, very pale and diffuse, joining the 
Marc Tyrrhenian to the Tiphys Fretum, and separating Eridania from 
Ausonia Australis. According to Schiaparelli, Maedtcr observed the 
Xanthus in 1830 and 1832. Lockyer drew it as diffuse in 1862, and so did 
Hokien in [875. From Milan, in 1877, it was adjudged as being visible 
more because of its breadth than because of its darkness, so that it was 
badly defined along its edges. Schiaparelli followed it in 1878 until the 
disk of Mars was reduced to 7". He saw it as a broad shading in 1879, and 
as a sombre band in 188 1-2. Ten years later, Schaeberle showed it as 
broad and conspicuous. I suspected traces of it in 1892 with an o m -io8 
telescope, and in 1894 from Juvisy with the o ni -24; then in 1909, from 
Meudon, I could distinguish it only as the strengthened, shaded border 

284 



of Ausonia Australis. At this time Hale photographed it as broad. To me 
it seemed broadened also in 191 1, with the o m -83; it was the same in 
1924, when I saw it clearly inclined to the meridian and lying toward the 
NNW (Fig 19). The same aspect was seen in 1926, though with a floc- 
cular appearance; in 1927 I saw it admirably with a magnification of 1 250 
with the o n, -83 refractor, on a 7"-8 disk. Cerulli noted in 1896-7 that the 
Xanthus is easiest to observe when seen obliquely. 

ZEPHYRUS. Greyish, ill -defined area on Elysium, going from the 
Cerberus to the Galaxias. It was noted as double by Cerulli, but single 
by Molesworth, from 1896 to 1899. Brown glimpsed it in 1898-9; so did 
1 in 1900-1, and Molesworth in 1903. 

References 

1. Maunder carefully considered this observation (Mars Report 1892, in Mem. BAA, 
vol. II, pp. 173-5) and was astonished at the visibility of Icaria in my o m, io8. This 
land was then very shaded — as in 1909, when it was not very different from Aonius 
Sinus. 

2. Fragments sur les corps celestes du systeme solaire, p. 153. 

3. Memoria I, p. 71. 

4. litis was shown by Terby (Arcofrrnphie, p. 86). 

5. This has been shown by Schiaparelli (Flamnwion, La planetc Mars, vol. II, p. 232). 

6. See mv note in Month. Not. RAS, vol. 69, 1908, p. 112, and Fig. 2 of Plate 4. 

7. FLAMMARION, La planetc Mars, vol. I, p. 385. 

8. Ibid, vol. 1, p. 449. 

9. Memoria 1 1 1, p. 54. 

10. Memoric della Soeieta degli spcttroscoptsti italiani, vol. XI, p. 26. 
It, Memoria VII, p. 38. 

12. Memoria I, p. 68. 



13. Nuove osservazioni di Marti-, 

14. Memoria II, p. Ho, 



P- 5* 



285 



The South Polar Zone 



mare australe (S, 1877). This is all the sea in the S glacial zone of 
Mars. In winter the snow extends down almost to latitude 6o s , and the 
sea is often veiled by whitish clouds. The Mare Australe was first drawn 
by Maraldi I in 1719, and it has been observed since then by all areo- 
graphers. Its intensity is less than those of the equatorial seas, as is seen 
on all drawings and photographs which show the S hemisphere. The 
variable colour of this polar sea has been described in various terms. In 
1862 Lockyer saw it as green above Thaumasia (e = 20°); in 1877 
Schiaparelli noted a tint intermediate between brick red and olive in the 
same region (e = i2o c ), and in 1879 he recorded an azure grey {e = 
—50°). From Meudon in 1909 I saw a brownish tone along the coast of 
Hellas (e — 358°); in 1924 I first distinguished a greenish grey (e = 
304"), but after 9 August (e = 32 1°) I saw it brown, as Baldet confirmed 
on the next night after I had notified him. At the same time Bidault de 
l'Isle observed a brown colour on the coast. Then, in 1926, it was green 
at first (e = 337 ) and then chestnut (e = 50°). 

According to Schiaparelli, a white spot was seen over Mare Australe 
in May and June 1888, at lat. -62 , long. 1 18 . 

depressiones hellesponti tVE. Group of sombre spots at the source of 
Hetlespontus. Schrceter drew them in 1798 as one mass, and Beer and 
Maedler and J. Herschel showed them similarly in 1830. Then, in 1862, 
Kaiser, j. Phillips and Knott saw here only one patch, while Lockyer 
recorded two; Kaiser drew a single object in 1864. Cruls in 1877, Niesten 
in 1879, again showed the region as very dark. However, it is very curious 
that Schiaparelli never noted this sombre area, though it was represented 

286 



by Hussey and Young in 1892, myself in 1894 (Fig 23), Eddie and 
Buchanan in 1907, and myself again in 1909, 1911, 1924 and 1926. With 
the o"'-83 I saw two strong patches here in 1909 (Fig 134). I confirmed 
this aspect in 1924, and also saw other dark patches. In this year, as seen 
from Meudon, Depressiones Hellesponticae appeared brown after 
22 August (e = 329°). They were also sombre and brown on 6 August 
1926 (e = 346 = ) and later (e — 48 ). 




Fig 134 Depressiones Heliespontic<e, seen as composed 0/ two dark 
masses, 14 October iqoq. (o m -8j refractor) 



MONS arGENTUS. At the time of the melting of the south polar snows, a 
brilliant mass can be seen to the E of Argyre II, as was noted by G, 
Fournier at long. 30 s , lat. —J0°. This accumulation of snow diminishes 
more slowly than the neighbouring ice, as if there were an elevated 
plateau — as has been suggested by Campbell. 1 The beautiful cape 
formed by this glittering mass was represented by Schiaparelli in 1877; 
Barnard, Schseberie, Hussey and Campbell in 1892 (e = 30 1° to 325 ); 
Barnard and Campbell in 1894 (e = 293" to 336 ); Eddie in 1907 
(e = 287 ); and Pease, Graff, G. Fournier, Bidault de l'Isle, Quenisset, 
Lyot and myself in 1924 (Fig 135). At this latter date, I followed the 
phenomenon, from Meudon, from beginning to end (e = 282 to 332 ). 
With the great refractor I saw the promontory as more brilliant than any 
other part of the snows, except for the white mass of Novissima Thyle ; 
it formed a strong projection on the contour of the cap, and it was 
flanked by gulfs, of which the left one opened on to Depressiones Helles- 
pontica:. These findings were confirmed by the photograph taken at this 
time by Hubble, 

The brilliant mass of Mons Argentus can be seen, with its cape, at 
least from e = 282 to 336 . 



287 







Pig *35 Topography of the south polar zone of Mars, in 1924. 
(o m -83 refractor) 



ARGYRE II (S, 1879). This is a (kserl island remote, poorly -defined 
and not very bright, lying in the meridianal glacial zone of the planet, 
about 500km to the S\V of the shores of Argyre I and 1600km from the 
coast of Thauinasia. It is larger than Novissima Thyle, and appears oval; 
its area is about twice that of Iceland. A mantle of snow and hoar-frost 
covers it in winter. Trouvelot was the first to draw it, in 1877; it was 
elongated along the parallels, but ill-defined. Schiaparelli observed it in 
1879, giving it as an extension of Argyre I. its K coast,' he wrote, 
'appears smoky ... on the other hand the \Y coast is sharp and 
brighter.'- In 1892 Keeler showed it connected once more to Argyre i, 
and Campbell and Barnard represented it in 1894 as beautiful, bright 
and large. With the o'"-83 I saw it without difficulty in 1911; it was 
extended and oblong, slowly degraded toward the K, and appearing well- 
defined in the N, less so in the W, and very feeble in the S (Fig 136). In 




-•'./.-■'- 




C M. A 



Pig '.ft I'ht ml island Argyre If, 6 December i<)ll. (o m -H.j refractor) 

1924, from Meudon, it appeared to me as floccular, particularly to the K; 
it was even larger than it had been in 191 1 . These descriptions were con- 
firmed by the photograph taken by Hubble wih the 2" l, 57 Mount Wilson 
mirror. 

Argyre II was badly defined in 1926, except on 18 November. The 
albedo is below that of Argyre I ; Schiaparelli commented on 'the feeble 
brightness' of Argyre II when on the central meridian/' and with the 
great refractor I always see it as strongly smoky. This is confirmed by the 
photographs. Trouvelot showed the band as reddish; Schiaparelli found 
it 'a disturbed red, and of slight brilliancy'.' 1 To me it seemed shady red- 
vermilion in igii, from Meudon; sometimes brick-red, sometimes 



288 



289 






greyish, during the latest pcrihelic opposition. 

From 1 8 to 23 August 1924, yellow clouds over this island hid it from 
me as seen from Meudon (Fig 137). 




Cut \ 



Fig ijj The retreat of the shotcs, uncovering the red soil of Argyre II, 
18 August i()>4. fo m 'Sj refractor) 

The yellow clouds sometimes give Argyre II an orange tint, as Lyot 
and I have shown. The island sometimes glitters very brightly when 
near the limb; this was first noted by J. Phillips in 1864, and then in 1 879 
by Schiaparelli, who frequently found Argyre II brilliant during the 
opposition of 188 1-2: 'similar to the polar snow, and splendid'."' After 
an interval of eight years, it was observed glittering on the limb in 1890, 
and this was also seen by Ntesten and Stuyvsert in 1892; in this year 
Keeler once noted it as bright when near the central meridian. In 1896-7 
it sometimes appeared very white to Cerulli. I never saw it luminous in 
1924 or 1926, but it was often glittering in 1928-9. Large white clouds 
often cover Argyre II during the bad season. 

A vast yellow cloud lying over Argyre II produced an amber projec- 
tion from the terminator on 8 December 1924. 

CHIronis frktcm. This is the strait to the W of Argyre II. 

DlA. In 1877 Schiaparelli suspected the existence of a very smoky 
island between Thyle I, Argyre and Thaumasia, because to him this 
part of the Mare Australe seemed less dark than the rest of the sea. I 
have found an indication of this half-tone on the drawings made by 
Secchi, Kaiser, Lockyer, Dawes, Trouvelot, Ftanunarion (Fig 70), 
Green, Burton, Dreyer, Xiesten, H olden, Barnard, Keeler, Campbell 
and others. I have given this island the name of Dia. Bubble's photo- 
graph reveals a slight brightening of the Mare at the 1924 position of the 
island. Bidault de l'Isle saw it well in 1924; and on 22 and 23 September 



290 







Fig 138 The circumpolar land of Dia, to the south of Thaumasia, on 
22 September KJJ4. (o m -8j refractor) 

of that year I noted a yellow patch in these latitudes (Fig 138) which 
appeared orange on 15 December 1926. 

Beer and Mscdlcr drew the region whitish at the limb in 1839; I saw 
the same phenomenon, with Phillips, in 1898-9 and also in December 
1928 and February 1929. 

On 6 December 1924 and 8 January 1925, with the o m '83, I saw Dia 
yellow and protruding from the terminator. 

thyle 1 (S, 1877). Large island, remote and foggy, comparable in area 
with our Borneo. It is very smoky, and extends to the S of Phaethontis, 
from which it is separated by the Palinuri Fretum. It is completely snow- 
covered in winter. Beer and Midler drew it as joined on to Thyle II in 
1830. It was shown in 1862 by Kaiser, Lockyer, J. Phillips and Lord 
Rosse's assistant, 8 and in 1877 it was shown by the Henry brothers, 
Terby and Green. Others have seen it since. Schiaparelli showed it con- 
spicuously oval in 1877, elongated along the parallel, and with blunted 
points to the E and the W. In 1879 'it was not round,' he wrote, 'but 
slightly pointed toward the E extremity', where there was a yellow cape. 7 
With the o m -83 I also saw an apparent E-W elongation, but it was very 
irregular, making a bay toward Ulyxis Fretum* and a cape pointed to the 
SW(Fig 139). 



* 1 had noted this detail with the o m -zc6 reflector several weeks earlier. 



291 




Fig ij(j The shaded south polar islands of Thyle I and Thyle II, tvilh 

Ulyxis Fretum and the Mare Chronium, on 5 November iqqq. 

(o m -8j refractor) 

The low albedo of this region was noted in 1862 by all the observers 
listed above. In 1864 Kaiser even showed Thyle I as more shaded than 
Electris and Eridania; but Schiaparelli did not show it as really shaded- 
off on his charts. To me the shading sometimes seemed very strong in 
1909, 1924, 1926 and 1928-9, greater even than that of Phscthontis. I saw 
Thyle I grey-violet in 1909, from Mcudon (e = 27 ); then reddish, in 
general very smoky, in 1924 (e = 33 8° and greater); and later in this 
opposition, slightly chestnut (e = 19 ), 

From time to time in 1924 yellow atmospheric veils made Thyle I 
seem orange or yellowish. On 14 October, with the o""^, it appeared a 
dull grey. It was smoky yellow in 1926. Thyle I appeared whitish on the 
central meridian on 10 October 1924. The island sometimes whitens 
when seen obliquely, as was shown on the drawings made by Galle as 
early as 1839. It can even appear as white as snow, and this is how Kaiser 
noted it on 3 January 1865. In 1877 and 1879 Schiaparelli sometimes 
observed it as remarkably bright near the limb, and in 1881-2 this was 
again noted from Milan, when the glitter came from a small part of the 
island — always the same part, incidentally. The Italian astronomer 
again saw Thyle I white at the limb in 1883-4, 1888 and 1890; this was 
confirmed by Cerulli from 1896 to 1899 and by myself from Mcudon in 
191 1. In October 1924 and January 1927 I saw a pale fog cover the island 
and its companion (Thyle II). In winter, Thyle I is often veiled by 
whitish clouds. 

ultimum pkomontokium. Cape at the S\V of Thyle L With the o n, 83, 
in 1909, I saw it as pointed, 

thyi.es mons. Probably a mountainous region, situated in the S part 
of Thyle I, on which — as Campbell has shown — the snow melts slowly. 



292 



A white patch was observed here by J. Phillips in 1864. Hussey, Camp- 
bell and Schsebcrle in 1892 (e = 313° to 319 ), Campbell in 1894 (e = 
310 ) saw here a cape formed by the polar snows. Eddie saw an isolated 
snowy mass in this position, in 1907 (e = 306 ). From Meudon I had an 
ex eel lent view of this tongue of ice in 1929 (e = 310 to 323°) (Fig 135). 
It was also well seen in the same year by Bidault de l'Isle. 

This brilliant snowy mass can be observed as a promontory between 
e = 301° and at least 323 . 

ULVXtS FRETUM (S, 1 877). Strait to the S of the Mare Chronium, 
separating Thyle I from Thyle II. In 1830 Beer and Msedler showed here 
a sombre patch elongated in a X-S direction. Schiaparelli described the 
channel as easily visible in 1877, and he reobserved it in 1879. It was 
subsequently represented by Gale and Eddie in 1892, and I was able to 
see it in 1894. However, in 1909 and 1924, with the o m -83, I found that 
it was very irregular— broad to the X, narrow and curved back toward 
the right in the S (Figs 135 and 139). Ulxyis Fretum was also seen in 
1924 by Bidault de l'Isle, From Meudon, it was badly defined in 1926, 
but dark in January 1929. 

On this straight the snows melt more quickly than on the neighbouring 
islands, and in 1907 Eddie showed a notch in the ice at longitude 210 
(e = 302 ). 

thyle II (S, 1877). 'Fhis is another large southern island, lying to the 
S of Eridania, from which it is separated by the Tiphys Fretum. It seems 
to be often covered with mist, and in winter it is whitened by the snows. 
Schiaparelli found it 'a little smaller, and nearer the meridian', than 
Thyle I. s Beer and Msedler, in 1830, showed it joined on to Thyle I; in 
1862, Kaiser saw it joined on to Eridania. 9 In this year it was shown by 
all those who also observed Thyle I, and it again appeared on the draw- 
ings made by the Henry brothers, Flammarion, Tcrby and Green in 
1 877. I n the latter year, the Milan astronomer drew it slightly elongated 
along the parallel, but with a blunted point to the S. To him the contour 
seemed the same in 1879. From Mcudon, in 1909, it appeared to me to be 
more definite than its sister isle, but also very irregular, with a cape 



293 



rounded to the E, and making the bay of Noti Sinus to the NE (Fig 139). 

Thyie II is of tow albedo, comparable with that of Thyie I. Kaiser, as 
early as 1862, showed it as smokier than Eridania, and this was con- 
firmed by Secchi, Lockyer, J. Phillips and Lord Rossc's observer; but 
Schiaparelli drew it as bright on his maps. The colour of Thyie II, 
yellow to Schiaparelli in 1881 -2, seems to me to be almost identical with 
that of Thyie I. 

Yellow clouds sometimes gave this land an orange tint in 1924, but it 
sometimes appeared greyish. It showed as whitish on the central meri- 
dian on 10 and 14 October. It was smoky yellow in 1924. From time to 
time Thyie II whitens when seen obliquely; as early as 1839 Galle 
showed it white at the limb, and this was confirmed by Secchi and Kaiser 
in 1862. Schiaparelli found it remarkably brilliant at the limb in 1877-8, 
and glittering in 1879; in 1 881 -2 this beautiful glitter came — as with 
Thyie I from a small part of the island. I confirmed this in 1926. 
Whitenings were also noted from Milan in 1883-4, >SS8 and 1890, 
Cerulli saw the same thing between 1896 and 1899, and so did I in 191 1. 
There was mist over Thyie 11 early in October 1924; and in 1926-7 it 
appeared to become more and more resplendent with the advance of the 
season and the approach of winter. 

Thyie II protruded from the terminator on 6 and 7 December 1926, 
as seen from Meudon. 

thyles coi-Lis. An isolated snowy mass was noted in Thyie II by 
Young in 1892 (e = 307 ) (Fig 140) and by Eddie in 1907 (e — 305°). 







Fig 140 Isolated snowy patch on Thyie 11, observed by Young on 
July 1892. (0 m -$8 refractor) 

Presumably it is a mountainous region. 

noti sinus. Bay at the NE of Thyie II. 1 detected it with the o">-83 in 
1909. (Fig 139.) 

notus. Streak, convex to the W. I observed it in 1909, from Meudon, 
on Thyie II (Fig 139). 

294 



promethei sinus (S, 1 877). Vast gulf at the W of Tiphys Fretum, be- 
tween the banks of Thyie 1 1 and of Chersonesus. Beer and Manlier drew 
it dark in 1830, as a broadening of Tiphys Fretum. It was again seen in 
1832. Kaiser 111 and Lockyer showed it well in 1862, as did Kaiser in 1864. 
Schiaparelli drew it still better in 1877, but he found it difficult in 1879. 
Then, in 1924, I found that the beak of Chersonesus was sometimes 
causing a reduction in the breadth of the gulf. Promethei Sinus can 
appear quite intense; Terby and Cruls represented it as very sombre in 
1877, Schiaparelli described it as shaded in 1881-2, and Buchanan as 
very dark in 1907. 1 sometimes saw it as intense in 1909, 191 1, 1924 
(Fig 135) and 1926, and in 1909 Hale's photograph showed it as slightly 
more shaded-orT than the Mare Australe. To Lowell, in 1894, the colour 
was at first blue (e — 301 ) and then brown (e = 332°). With the 
o m -2i6 reflector in 1909 I first saw it as blue (e = 340"), but it was dark 
brown in 1924 after 2 September (e = 337 ), and chestnut in 1926 
(e=n°). 

A white patch lasting for i\ months was seen from March to June 1886 
by Schiaparelli, at long. 253 , lat. — 55 , on Promethei Sinus. 

somni depressio. Sombre patch, which I observed from Meudon in 
1924 to the E of Novissima Thyie (Fig 141). It was brown at this time 
(e = 36°). During the shrinking of the south polar snow-cap, Somni 
Depressio appears as a dark gulf in the cap to the left of Novissima Thyie, 
covered with ice and detached from the main mass of snow. 




Fig 141 The south polar island of Novissima Thyie, observed on 
8 December n/24. (o m -8j refractor) 

novissima THYLE (S, 1879). This island — -the most southerly of all the 
polar lands — is lost in the glacial snows, as broad as Hellas and to the 
SW of it. It is separated from Hellas by a 700-km strait. It is nookm 
from Noachis, 1400 from Argyre II, 1500 from Thyie II and 900 from 



295 



the sooth pole of Mars. Its area is greater than those of our Lakes 
Victoria and Albert; a blanket of snow covers it in the cold season. This 
is what Schiaparelli said of it in 1879: 'On 2 December ... I observed 
a small island in transit on the central meridian, less extended than the 
polar snow, and appearing almost round . . . The longitude of this 
island would be 335^-1, and the polar distance iq°-2 ... On 7 Decem- 
ber, the longitude of the central meridian being 240 , I saw the island to 
the right of the polar cap; in contact with it and with the edge of the disk, 
a yellow patch appeared to extend toward the Promethei Sinus . . . 
Finally, on 31 December, with the central meridian at 340°, I noted a 
small white patch between Hellas and the polar snow. . . , These three 
observations lead me to suppose that there is only one island, lying a 
little to the N of where Novissima Thyle is shown on the map.' 11 

I observed this island more than once in 1924 with the o nu 83; it was 
irregularly round, very smoky (Fig. 141) and in colour a remarkable- 
brick vermilion rose. It presented the same aspect in 1926, though less 
clearly. 

In 1924 the yellow clouds which sometimes covered Novissima Thyle 
gave it an orange tint. On 13 and 14 November 191 1, from Meudon, I 
noted a disturbance in the S polar regions of Mars, in the form of an im- 
mense white cloud with very broken-up borders, covering up Novissima 
Thyle and the neighbouring region and advancing toward the E. 
Schiaparelli in 188 1-2, Flammarion and Stanley Williams in 1890, and 
Cerulli in 1896-7 observed Novissima Thyle white or brilliant when on 
the limb. It was glittering in the S in December 1928. In winter, it is 
often lost in the white mists. 

novus mons. Probably an elevated plateau on Novissima Thyle, on 
which, according to Campbell, the snow melts more slowly than else- 
where in the area. Evidently there is a thick crust of ice here. Novus 
Mons can be seen detached from the rest of the polar cap, from which it 
is separated by a sombre channel (Fig 142). As early as 1798, Schroter 
showed here a white patch by the side of the southern snow, and in 1845 
Mitchel observed something analogous. Here arc the most recent 
observations : — 



296 






Date 


e 


Observer 


Snow on Novissima Thyle 


1877 


341-346 


Green 


Very brilliant point. 


1892 


301-308 


Campbell 


Very brilliant area of the S. polar cap, 
near long. 330 , lat. — 65 . 


1892 


305 


Hussey 


Cape of the cap, near long. 330 , lat. — 65 . 


1892 


3H 


Molesworth 


Snowy mass, detached from cap. 


1892 


321-328 


Keeler 


Do., near lat. 330", long. — 65 , 


1892 


327 


Campbell 


Snowy detached mass, near lat. 325°, 
long. -75 . 


1892 


328 


Scha:berlc 


Do., near long. 31 0°, lat. —75°. 


1894 


3°3 


Campbell 


Large brilliant cape of the cap, near long. 
320°, lat. -71°. 


1894 


304 


Lowell 


Two brilliant points in the cap, near long. 
280' and 290 , lat. — 76 . 


1894 


308 


Lowell 


Snowy mass, detached from the cap. 


1894 


340-347 


Barnard 


Do. 


1909 


333 


Jonckheere 


Do. 


1909 


334 


G. Fournier 


Do. 


1909 


336 


Antoniadi 


Do. ; long. 308°, lat. -79 (Fig. 142). 


1909 


336 


Quenisset 


Do., long. 330°, lat. — 70 . 


1909 


341 


Antoniadi 


Dull yellow point, well detached from the 
cap, near long. 320"', lat. —75°. 


1924 


329 


Lyot 


Snowy mass detached from the cap; long. 
320 , lat. -73 . 


1924 


327-333 


Antoniadi 


Do. 


1924 


33° 


Mine. G.-C. 








Flammarion. 


Do. 


1924 


3S3 


G. Fournier 


Do. 



As Flammarion and I showed in 1909, these data establish that the 
separation of Novissima Thyle from the cap is a regular phenomenon of 
the melt of the southern polar snows of Mars. It can be seen between 
e = 308 s and at least 330°. It never occurs at exactly the same helio- 
centric longitudes, and is subordinate to the local meteorological condi- 
tions and to variations in the intensity of the Sun's radiation. Thus in 
1892 and 1894, near sunspot maximum, it was observed after longitude 
314" and 308 s , and in 1909, a year of mean solar radiation, and in 1924, 
a year after maximum, it was seen later. In these two latter years I com- 
mented that the mass of snow detached became dull and yellow before 



297 




Fig. 14J Xoi'issima Tliyle covered with snore, hut detached from the 
ices 0/ the south pole, .'5 August kjimj. {o'"-2i(-> reflector) 

disappearing; however, the yellow tint may well have been due to 
clouds. 

SiSYPHi DEPRESSIO. Dark patch of the Mare Australe, to the VV of 
Novissima Thyle. I observed it with the o m, 83 in 1924 and 1926. It then 
became brown (e ™ 36 and 48°) (Fig 141). 

rima australjs. Broad irregular streak, dark and concave to the S, 
going from Deprcssio Hctlesponticse to Ulyxis Fretum, and which 
separates Novissima Thyle from the rest of the melting snows. It was 
observed by W. II. Pickering, Young, Schseberle, Hussey, Campbell, 
Gale and Molesvvorth in 1892; by Pickering, Campbell, Hoklen and 
Lowell in 1894; by Jonckheere, G. Fournicr, Quenissct and myself in 
1909, and by myself from Meudon in 1924. With the o m *83 it was striking 
in the latter year, and appeared very broken-up, knotty, and degraded 
toward Depressio Hellesponticee; it was clearly oriented toward the 
Margaritifer Sinus (Fig 135). Its nature, like those of the two other 
neighbouring streaks, differs from those of the sombre patches of these 
regions, since snow is not held there. 

rima brevi.s. Short dark streak to the E of Novissima Thyle, flowing 
out at Somni Depressio. It was observed in the snows by Lowell in 1894, 
G. Fourner in 1909, and myself in 1924 (Fig 135). 

depressio magna. Large dark patch of the Mare Australe, about io° 
from the south pole, and lying at approximately longitude 270 . It was 
seen as an eccentric blackish spot in the south polar snows when they are 
extended, and also on patches of the Mare which are dark after the 
retreat of the ices, by many observers since the time of Mitchel, who 
recorded them in the middle of the snows in 1845. Barnard, Hussey, 
Schaebcrlc and Young showed them in the cap in 1892 (e = 296 to 
315"), and Barnard, \V. H. Pickering and I ^ well in 1894 (e = 293 to 






323'). G. Fournicr drew them excellently in the snow in 1909 (e = 32 1°), 
and I often observed them similarly in 1924, from Meudon (e = 292 to 

3 21 ) (Fig 135). After the melting of the ices in these latitudes, I dis- 
tinguished them as dark on the brownish floor of the Mare Australe on 

4 September 1924. Barnard saw Deprcssio Magna reddish in the snows 
in 1892; I saw it greyish, often veiled, in 1924. 

This remarkable patch, whose nature is different from that of the Mare 
Australe inasmuch as snow cannot persist on it, can therefore be observed 
between e = 292 and at least 323 . Can it be a great polar lake, and can 
the neighbouring cracks be open channels? 

depressio parva. Another fairly dark patch in the south glacial zone, 
of the same nature as the preceding one, and a dozen degrees from the 
pole. It lies to the S of Thyle I. From .Meudon, in 1924, I observed it 
from June to August (e = 294 to 321°) (Fig 135). 

rima angusta. This is a dark streak in the S polar region, very sinuous, 
and directed toward Thaumasia. It can be seen in the snows. It was first 
observed by Schaebcrlc in 1892, and then by Douglass in 1894; I saw it 
as wavy in 1909, from juvisy, with the o m -2i6 reflector; and in 1924, 
with the o m -83, I noted it as extremely irregular, sinuous, and almost 
black (Fig 135). In the latter year it was excellently drawn by Graff. 

hypernotius MONS. Probably an elevated mountain or plateau,* where 
the melting polar snow clings to the Rima Angusta (Fig 135). In 1877 
Schiaparelli drew it as of triangular form, and 1 confirmed this in 1909. 
It is rare for the snow here to disappear completely; but it did so in 1894, 
at a time when solar activity was considerable. 



• 'It is probably a vast elevated island," wrote Flammarion in 189a, 'as otherwise the 
ice would melt, perhaps completely. 1 ' 3 



References 



I. 


FLAMMARION, 


La 


planete Mars, 


vol. 


11. 


P 


3. 


Mi'NinriM 11. p. 68 














.»■ 


FLAMMARION, 


up 


cit., vol. I, 


P- 


440 






4 


Memoria II, p. 6H. 














5- 


Memoria III, p, jj 














6. 


SCHIAPARELLI 


M 


emoria I, p 


78- 






7. 


Memoria II, p. Si, 















184. 



298 



299 



H. Mtmoria I, p. 78. 

9, Memom I, p. 7M, 

10. Mamorii I, p. 04. 

] 1 . Mi'iin jriLL II. p. OO. 

12. Dull, (if la Soc. Astr. dc France, vol. 23, p. 305; Jnl. Brit, Aslron. Assoc, vol. 10, 

p. 4*9. 

13. FLAMMARION, op. cit., vol. I. p. 544, 



300 



The North Polar Zone 



ortygia (S, 1 886). Smoky continental region in the N polar zone, 
bounded by the Callirrhoe to the S, the lascartes to the W, the Lacus 
Hyperboreus to the N, and the Kison to the E. The light shading of 
Ortygia was shown on the sketches made as early as 1837 by Beer and 
Msedlcr and in 1839 by Galle; it has since been observed by Secchi, 
Trouvelot, Flammarion, Schiaparelii and myself (Figs 51 and 65). 
Lowell and Lampland photographed it in 1905. From Milan in 1888 the 
colour of the ground here appeared dark yellow. The N part of Ortygia 
is buried under the snow and the white clouds in winter. 

Burton in 1871, and Gale and Molesworth in 1903, saw a white patch 
on Ortygia; in 1888 Schiaparelii sometimes noted it as bright. Ortygia 
does not often whiten when seen near the limb, but the phenomenon was 
observed by Secchi in 1858 and by Schiaparelii in 1886. 

On 19 October 1909, Le Morvan took a photograph in violet light, 
showing a vast white cloud over Ortygia. He was using the great coude 
of the Paris Observatory. 

baltia (S, 1883-4). I n ' s ' s a ' ar f e i s l an d, comparable with the Thyle 
Insula; in the south ; it is very strongly shaded, and it is very variable both 
in appearance and in intensity. It lies to the N\Y of the basin of Mare 
Acidalium. It was shown by Msedler from 1837 to 1841 and by Galle in 
1839, and confirmed by Secchi in 1858. It is curious that Burton showed 
no trace of it in 1871 (Fig 93) or in 1873. Schiaparelii, Trouvelot and 
Lohse represented Baltia as quite dark in 1883-4, and from Milan it was 
again seen in much the same form until 1890 (Figs 94 and 95). 1 noted it 



301 



as sombre in 1898-9 (Fig 97), much feebler in 1 900-1 (Fig 98) and more 
intense in 1903 (Fig 99). In the latter year, the shading was also shown 
by Attkins, Gale, Corder, W. J. Hall, Molesworth and Phillips. Lowell 
and Lampland photographed it as pale in 1905, while Ward showed it as 
shaded. It appeared quite dark to me in 19 18. Fournier showed it as 
lighter in 1920; Gale and Attkins drew it as a half-tone. Schiaparelli saw 
Baltia as yellow from 1883 to 1886, generally brownish yellow in 1888; 
VV. J. Hall saw it brick red in 1903, and to me it seemed bluish grey in 
1918. 

The white streak noted from Milan in 1881-2, going from the northern 
snows to Thai-sis, passes through Baltia. Moreover, Gale, Attkins, 
Molesworth and others noted a bright patch in the E part of Baltia in 
1903; and Ward in 1905, Briault in 1915-6 and Thomson in 1918 saw 
Baltia crossed by a bright streak running along the parallel. 

Liais drew Baltia as bright when seen at the limb in i860. It is often 
covered by clouds in winter. 

A vast, glittering white cloud in this area on 19 October 1909 was 
photographed in violet light by Le Morvan. 

aspledon lacus (L, 1900-1). Sombre patch, observed by Lowell be- 
tween 1 900 and 1905 in the region NW of Baltia. 

aualos (S, 1888). Very smoky and variable island, enclosed between 
Baltia and Nerigos. It disappears under the ices during the bad season, 
and makes up part of the shading to the W of the Mare Acidalium drawn 
by Beer and Manlier, Galle and other observers. The greyness was also 
seen by Secchi in i858,*but was not shown by Burton in 1871 (Fig 93) or 
1873; however, from Milan it was nearly always described as intense. In 
1890 Schiaparelli saw it as darker than Baltia or Ncrigos. Feeble to me in 
1900-1 (Fig 98), it seemed a little stronger in 1903 (Fig 99); this was 
confirmed by Attkins, W. j. Hail and Molesworth. Ward showed it as 
shaded in 1905, and I saw it dark in 1918. In 1888 Schiaparelli found it 
much browner than Baltia or Ncrigos. In 1903 Gale and Molesworth 
saw here a bright patch following the Lacus Hyperboreus. As with other 
lands round the pole, Abalos is often covered with white clouds during 
the cold season. 






nerigos (S, 1883-4). Another island, strongly grey and very change- 
able, in the basin of the Mare Acidalium, As with Baltia and Abalos, it is 
shown on the drawings made by Beer and Maedler, Galle and Secchi, 
but, like Baltia and Abalos, it was omitted by Burton in 1871 (Fig 93) and 
1873. Trouvelot showed it as distinctly shaded-off in 1883-4, as did 
Schiaparelli from this time until 1890 (Figs 94 and 95). To Terby it 
seemed less dark than Baltia in 1888. I found it feeble in 1 900-1, but 
more marked in 1903, as did Gale, Molesworth and Phillips. Ward drew 
it as smoky in 1905; so did I in 1918. G. Fournier showed almost nothing 
of it in 1920, but Gale and Attkins described it as shaded, and to Danjon 
at this time it appeared very uneven in tone. From Milan it seemed 
yellow from 1883 to J 886; brownish- yellow, generally moderately 
tinted, in 1888. 

As early as 1704, Maraldi I drew Nerigos white at the limb in winter. 
I confirmed this appearance 220 years later. 

Mj>edtis pall'S (S, 1886). This is a feeble marsh lying to the W of 
Nerigos. It was shown on sketches made from 1837 to 1841 by Masdler. 
Bceddicker showed a shading here in 1881-2; Schiaparelli saw it diffuse 
in 1883-4, as a ' ar g e bl^k patch in 1886, less prominent in 1888 (Fig 
144) and smoky in 1890. Masotis Palus appears dark on Terby's drawings 
of 1888. I glimpsed it as pale from Juvisy from 1898 to 1901 (Fig 143); 
Danjon drew it as confused, though quite obvious, in 1920, With the 
o ni -83 I saw it as pale indigo at the boundary of the polar snows on 4 and 
8 February 1929, and also in March of the same year. 




e M. 4 



14J Mreotis Palus, at the edge of the northern snoivs, on 
23 January tgoz. (o m -24Q refractor} 



lacus hyperboreus (S, 1 886). A lake, very remarkable because of its 
apparent blackness. It is larger than our Lake Nyanza, and borders the 



302 



303 



north polar cap. It lies several degrees from the pole, between longitudes 
io° and 90 , and is very obviously detached from the polar ice. In 1886 
Schiaparelli wrote : "The Hyperborean Lake was absolutely black, and the 
neighbouring very luminous regions of Ortygia and Ierne— and, even 
more so, the polar snows — made a vivid contrast with it, despite its small 
size and the marked obliquity of the view. Dr Terby observed it . . . 
on 3 May, and here, at Milan, it was very well seen again on ... 7, 8, 
9 and n May with the i8in refractor; the apparent diameter of the 
planet was between 9" and 10". 1 Then, in 1888, 'the Hyperborean Lake 
was perhaps less extended in latitude, but it occupied a much greater 
range of longitude than it had done in 1886, since it had invaded a part of 
what was then described as the island of Ierne. It was always very black, 
M much so as the Marc Acidalium' 2 (Fig 144). In 1888 Terby drew it as 




Fig 144 The Lacus Hyperboreus on ijj May i8H8, according to 
Schiaparelli. (o m -4<) refractor) 



dark, but not black. It was not seen at all from Milan in 1890, since it 
was veiled by yellow clouds. In 1900-1 Molesworth saw it encroaching 
upon the polar snows. Attkins found it very sombre in 1903, when Gale 
described it as follows: 'A very dark patch . . . almost black ... it is 
without doubt the most sombre patch that I have ever seen on Mars.' 
Molesworth saw it 'darker than anything on the disk, a little like a pool 
of ink' on 27 March; the contour toward the Mare Acidalium appeared 
diffuse. In 1903 Phillips saw it as 'a very sombre and very large widening 
of the polar band'. Lowell saw two small patches here in 1903 and 1905, 
adjoining the lake, which was 'the most sombre of the permanent 
patches'. 3 Millouchau drew it as much less black or extended in 1903 
U'iR 55). an d tr| is was confirmed by Phillips in 1915-6, Briault, 

304 









Thomson and Phillips in 19 18, and G. Fournier, Gale and Phillips in 
1 920. 

Schiaparelli found that the Lacus Hyperboreus encroached on the 
polar snows in 1883-4 0''f? 1 5 % as ^ tne > ce tr »erc were melting more 
quickly than that upon the neighbouring lands/ 1 This was confirmed by 
Douglass and Molesworth in 1900-1 and by Lowell in 1903. 

The lake was almost always invisible in 1905, and on 21 May 1918 I 
could see no trace of it with A. Barbier's o nl -32 reflector. 

scandia (S, 1886). Slightly greyish continental region, limited by the 
Eurotas to the S, the Hebrus to the W, the llissus to the N and the Palus 
Maeotis to the E. Maedler and Galle saw it strongly shaded in 1839, and 
so did Maedler in 1841. The half-tone was again observed by (among 
others) myself in 1900-1 and 1916, and by Danjon in 1920. 

Scandia was seen to whiten when seen near the limb by H. Wright in 
1905, Eddie in 1907, and myself from Meudon in 191 1, 1924 and 1926. 

ARSENius lacus (S, 1883-4). This is a lake of considerable importance. 
It lies in the polar wildernesses, around latitude 70°N, and is larger than 
our Great Bear Lake; it is situated NYV of Scandia. Schiaparelli observed 
it in 1883-4, and described it as slightly smaller than Propontis; in 1886 
it seemed to him to be extended, very black, slightly elongated N-S, 
and diffuse to the W, though sharper to the E. Subsequently, in 1888, 
Arsenius Lacus was easily seen from Milan, but it was smaller in 1886 




Fig. 145 Arsenius Lacus, Propontis and Copah Palus, on 21 February 
IQOI. (o m -240 refractor) 



305 



(Fig 144) and in 1890 Schiaparelli could not sec it at all. Cerulli observed 
it elongated in an E-W direction in 1898-9. To me it appeared large and 
intense, though rather diffuse, front Juvisy and Paris from 1900 to 1903 
(Figs. 127 and 145); at this time Gale found it forked and very dark. 
Subsequently Lowell observed it in 1905, and Danjon and G. Fournier 
in 1920, 

Molesworth saw Arsenius Lacus as sombre, and notching the polar 
snows, in 1 900-1. 

1 erne (S, 1886). A land which is perhaps less shaded than the others 
round the north pole. It is bounded by the Ilissus to the 8, the Magncs 
to the W, the outlying polar areas to the \, and the Hippalus to the E. 
J erne was shown as shaded on the sketches made by Beer and Manlier 
and by Galle between 1839 and 1841. However, Schiaparelli showed it 
bright yellow in 1886, and always luminous in 1888. To me in 1 900-1, 
and to Danjon in 1902, it seemed lightly smoky. Ierne is whitened by the 
snow and the clouds in winter. 

A bright patch on lerne, near the north polar ice, was seen by Schia- 
parelli in 1888 and by Lowell and Molesworth in 1903. 

deucalidonius lacus (S, 1888). Lake lying to the N of Arsenius Lacus, 
several degrees from the north pole of Mars. It seems to be larger than 
our Lake Tanganyika. Schiaparelli did not observe it until 1888; it then 
had the aspect of a sombre basin in contact with the polar snows, quite 
sharp, and by no means inferior to Lacus Arsenius (Figs 144 and 146). 




Fig 146 Deucalidonius Lacus, on 1 J June 1888, according to Schiaparelli. 

(o'"-4y refractor} 

Millochau and Molesworth drew it dark in 1903 ; so did Thomson in 
1918 and G. Fournier in 1920. 

Deucalidonius Lacus was not always seen from Milan in 1888, and it 
was scarcely visible in 1905. 

306 






lemuria (S, 1886). Greyish continental region, limited by the 
Cephissus to the S, the Cydnus to the W, the polar regions to the N, and 
the Magnes to the E. Beer and Maedlcr, and Galle, drew it shaded be- 
tween 1839 and 1841 , as did Trouvelot in 1873, myself between 1900 and 
1903, and Danjon in 1920, Snow covers the ground here in winter, and 
the sky is often covered with clouds. 

PANCHArA (S, 1886). Smoky land to the S of Lemuria, greyer than 
Cebrenia, and bounded by the Gyndes and the Granicus to the S, the 
Cydnus to the W, the Ccphissus to the N, and the Hebrus to the E. The 
shading was drawn by Beer and Msedler, and by Galle, in the first half of 
the 19th century; it was then indicated by other observers, including 
Seech i, Trouvelot, Terby (Fig 149), Millochau (Fig 147), Danjon and 
myself. Lowell and Lampland photographed it in 1905. 




Fig 14J The shaded Panchaia, with the Casius, in 1 903, according to 
Millochau. (o m -83 refractor) 

A white streak was seen here by Holden in 1888. Schiaparelli de- 
scribed the surface of Panchaia as bright. Terby saw it whiten when near 
the limb in 1875, and so did I in 1892. Vast clouds can be observed here 
during the bad season. 

uchronia (S, 1886). Another continental region, grey and very 
extended ; it is bounded by the Heliconius to the S, the Argaeus to the W, 
the polar regions to the N and the Cydnus to the E. Uchronia has been 
shown as a half-tone by many observers, including Beer and Maedler, 



307 



Galle, Seech i, Burton, Trouvelot, Terby, Millochau, Danjon and myself 
( F 'g '45)- Jt ' s whitened to the N by the ice in the cold season. 

Schiaparclli observed a large bright patch here in 1888. To me, in 
1925, Uchronia appeared luminous when seen on the limb. Clouds hide 
it in winter. 

On 16 April 1896, Molesworth noted a small projection on the 
terminator at Uchronia. 

copais palus. Vast variable marsh to the N of the Boreosyrtis. Traces 
of it are found on the sketches made by Mardler in 1841, and it was feebly 
indicated by Trouvelot in 1873. Schiaparclli noted a large sombre lake 
here in 1888, lost later in the gemination of the Casius. Copais Palus 
seemed very extended and diffuse to me in 1 900-1, and at this time the 
Fournicr brothers saw it with an o"»-io8 telescope. Millochau showed it 
small and sombre in 1903, when to me it appeared feeble. I again saw it 
diffuse in 1915-6; in 191 8 and 1920 Quenisset described it as well- 
developed. 

geminus pons. Small lake, drawn by Schiaparclli in 1888 (Fig 148) and 
by Lowell in 1903 in the N part of Cecropia, near long. 270°, lat. +80°. 
G. Fournier observed it in 1920. The notch in the snows seen by Burton 




Pig 148 Frigoris Pons on 27 May 1888, according to Schiaparelli. 
(o n -4<) refractor) 

on 13 March 1882 seems to have been produced by Geminus Fons. 

frigoris fons. Another small lake in this neighbourhood, observed by 
Schiaparclli in 1886 and 1888 at long. 330°, lat. +82°(Fig 148). Lowell 
confirmed it in 1903 and G. Fournier in 1920. 

cecropia (S, 1888). Continental region, smokier than Dioscuria, and 
lying between the Pierius to the S, the Kison to the W, the polar regions 
to the N and the Argaeus to the E. The shading here was drawn by— 






among others — Beer and Maedler, Galle, Secchi, Trouvelot, Flammarion 
and Millochau. I observed it from 1900 to 1903 (Figs 51 and 65) and in 
19 1 5-6; Lowell and Lampland photographed it in 1905. In the bad 
season, the N part of Cecropia is buried in snow. 

In 1888 Schiaparelli saw a white patch on Cecropia, near the north 
pole. He showed the region whitish in July 1888, and Molesworth noted 
a bright patch here in 1903. With the o m -83, in 1925, I saw Cecropia 
white when near the limb. White clouds frequently appear here in the 
cold season. 

omphales fons. Small lake, noted by Molesworth in Ortygia in 1899, 
and seen by him until 1903. The position is near long. 352 , lat. +67°. 

olympia. This is a massive mountainous area in the N glacial zone, 
analogous to the Montes Argenteus, Thyles, Novus and Hypernotius in 
the other polar zone. At Olympia, the melting of the snow heaped up in 
winter proceeds more slowly than in adjacent areas. It lies to the X of 
Lcmuria, on the 80th parallel. Olympia is detached from the northern 
snows, and is separated from them by a sombre channel, just as is 
Novissima Thyle in the S. At this time the polar cap appears double. The 
relevant observations are as follows: 



Date e° Observer 

1858 260-284 Secchi 



1888 215-236 Perrotin 
1888 215-253 Schiaparelli 
1888 217 Terby 

1 90 1 187-209 Lowell 
1903 180-213 Millochau 
1903 181-209 T. E. R. Phillips 
1903 194-220 Lowell 
1903 195-230 Molesworth 
1918 166 and over Briault 



Aspect of Olympia 
The snowy polar patch appeared 
'certainly double, and made up of two 
patches touching each other'. 
Olympia is separated from the N cap. 

Do. (Figs 144 and 146) 

Do. (Fig 149) 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 



As I demonstrated in 1910, 5 these data establish that the separation of 



308 



309 






Olympia from the cap is a constant seasonal phenomenon of the melting 
of the northern polar snows of the planet. It starts to become visible 
about [&5 = heliocentric longitude, and it seems that it can be followed up 
to 280°. It was observed for longer than this in 1888, a year of solar 
minimum, and for a shorter period in 1903, at the time of solar maximum. 
rima uorealis. Broad dark crevasse, separating Olympia from the rest 
of the snows. Seech i was the first to observe it, in 1858 (Figs 144, 146 and 
149), 




Fig 149 Doubling of the north polar shows, due to the presence of Olympia, 
on /J May 1888, according to Terhy. (o'"-Joj refractor) 

rima tenuis. Fine crevasse, noted by Schiaparelli in 1888 in the 
northern snows, running almost parallel to the meridian from 150° to 
330 . Douglass reobscrved it in 1 900-1. 

depressio borea. On 1 3 March 1882, Burton suspected 'a minute 
sombre point at the centre of the (northern) snow'. 8 We may have con- 
fidence in this excellent Irish observer, and so no doubt the object does 
exist in these regions. 



IRREGULAR STREAKS AND FINE DETAILS 

adonis (S, 1888). Straight line glimpsed by Schiaparelli between 
Stymphalius Lacus and Dcucalidonis Lacus. 

argil's (S, 1888). Straight line glimpsed by Schiaparelli between 
Copa'is Palus and Rima Borealis. 



310 






ARiON (S, 1886). Band noted by Schiaparelli from 1883 to 1888 be- 
tween Arsenius Lacus and Lacus Hyperboreus. To him it appeared 
broad and black in 1886. 

ARIUS. Vague streak on Ortygia, between Callirrhocs Sinus and the 
Kison. It was drawn as diffuse by Trouvelot in 1873, Molesworth from 
1900 to 1903, and Danjon in 1920. 

Cadmus (S, 1888). Line glimpsed by Schiaparelli in 1888 and 1890, 
between Coloe Palus and the Lacus Hyperboreus. 

chdron (S, 1886). Vague, very feeble band between Arethusa Lacus 
and the Mare Acidalium. Lohse saw r here a border of the shading to the 
N, in 1883-4; at this time Schiaparelli showed the Cedron as linear, as he 
also did in 1886. Molesworth drew it as broad and pale in 1903. 

CEPHISSUS (S, 1886). Diffuse streak, going from the Arsenius Lacus to 
the Cydnus. Maedler showed traces of it in 1841. Schiaparelli saw the 
Ccphissus very broad in 1886; at this time Denning saw it as diffuse, as 
he also did in 1903. In 1905 Ward and Phillips described it as broad, very 
ill-defined, and vague, 

choaspes (S, 1888). Nebulous band, apparently joining Lacus Stym- 
phalius to Lacus Arsenius. Schiaparelli represented the Choaspes in 
1888, and from Juvisy I glimpsed it as broad, floccular and pale in 
1900-1 . Molesworth saw here a streak 4 broad, making up the border of 
a shading, in 1903. Phillips made it 3 broad, and found it to be feeble. 
Ward showed it as broadened in 1905 ; Danjon, in 1920, showed it as the 
border of the grey area. 

cydnus (S, 1888). Band glimpsed by Schiaparelli between Sithonius 
Lacus and Geminus Fons. It was seen as single from Milan in 1888, but 
as double in 1890. In 1903 Molesworth saw it 3 broad, diffuse and 
knotty. 

enipeus (S, 1888). Line glimpsed by Schiaparelli in 1888 between the 
Lacus Arsenius and the Cydnus, where it is prolonged by the Pyramus. 

erigone (S, 1888). Straight line glimpsed by Schiaparelli in 1888 be- 
tween the Lacus Hyperboreus and the Lacus Castorius. The Erigone 
has never been observed under good conditions. 

hebrus (S, 1888). Quite a strong band, between the Lacus Castorius 
and the Lacus Arsenius. Schiaparelli glimpsed the Hebrus as double in 



311 






1 888 (Fig 144), and Molesworth observed it rather diffuse from 1898 to 
1903 — darker in the latter year, as was confirmed by Phillips. In 1903 
Millochau saw it only as the edge of the shading of Panchaia. 

hippalus (S, r886). Broad streak. To the W it forms the boundary of 
the shadings of Nerigos and Abalos, and from here it flows under the 
Lacus Hyperboreus. It was in this form that Maedler represented it in 
1837 and 1839. Schiaparelli showed the Hippalus as broad and reason- 
ably dark from 1883 to 1890, making up the strengthened boundary of 
the greyness of the two islands of Nerigos and Abalos. I noted it as the 
border of Nerigos in 1 900-1 (Fig 98); it was also seen in 1903 by Moles- 
worth, who described it as feeble. With Barbier's o m 32 reflector, I could 
see almost nothing of it in 19 18. 

In 1900- 1 Danjon saw the Hippalus first as a crack in the polar snows, 
and then as a greyish band. 

iaxartes (S, 1 88 1 -2). Broad, sombre streak. To the E it borders the 
grey areas of Baltia and Abalos, thereby making up the N prolongation 
of the Mare Acidalium. The Iaxartes was shown by Beer and Maedler, 
as early as 1837, as the boundary of the greyness to the right. To Gledhill 
and Burton in 1871 it appeared broadened and blackish (Fig 93), forming 
the 'pear's tail' of the Mare Acidalium; it looked the same to Burton in 
1873, though in this year Green and Terby saw it only as the border of 
the penumbra of Baltia. The Iaxartes appeared intense to Schiaparelli 
in 1 88 1 2 and sombre in 1883-4, when the Italian astronomer compared 
it with a true strait or sea-arm rather than a canal. In 1886, from Milan, 
it was first seen as broad and smoky; later as narrow, black and very fine, 
like a pen-stroke (Fig 94). In 1888 Schiaparelli drew it as rectilinear, 
broad and sombre (Fig 95); in 1890, as broad, dark and shaded-off. From 
Milan the Iaxartes has always been seen as the intensified border of 
Baltia and Abalos; in 1SS8 Terby could see only the border, without the 
actual streak. In 1896-7 the Iaxartes appeared Very sombre to Moles- 
worth; in 1898-9 it was diffuse, and visible on a disk of Mars reduced to 
5"-6. It was then 4 broad; in 1 900-1 it darkened gradually, and was 2° in 
breadth, and very sombre, in 1903. I glimpsed it as broad, intense and 
diffuse from Juvisy in 1 900-1, limiting the shading of Baltia to the SW 
(Fig 98); I had the same impression in 1903, though in this year Phillips 



312 



saw it only as the boundary of the shading to the right. Ward in 1905, 
and Phillips in 1906, again saw it as the boundary of the greyness of 
Baltia. In 1918, with Barbier's o m 32 mirror, I saw it on more than one 
occasion as the boundary of Baltia; but it weakened to the point of dis- 
appearance well before reaching the northern polar regions of the planet. 
Schiaparelli, in 1884 (e ■ 134°) and Lowell in 1897 (e = 95 ) saw the 
Iaxartes as a crack in the N polar cap (Fig 150). 







Fig iso The Iaxartes and the Lacus Hyperboreus breaking into the snowy 

northern cap, on 5 February 1884, according to Schiaparelli. 

fo m -2i8 refractor) 

idalius (S, 1888). Band glimpsed by Schiaparelli from 1886 to 1890, 
between the Lacus Sithonius and the Lacus Deucalidonius. 

iLissus (S, 1888). Streak glimpsed by Schiaparelli from 1883 to 1888, 
joining the Palus Masotis to the Lacus Arsenius. 

kison (S, 1886). Genuine broad band, continuing the Euphrates- 
Arnon as far as the N glacial regions of Arethusa Lacus and Lacus Hyper- 
boreus. Traces of the Kison can be seen on Seech i's drawings of 1858. 
Schiaparelli observed it as black and single in 1886, but double and 
somewhat displaced to the W in 1888 (Fig 95). In 1899 Molesworth 
glimpsed it on a disk of Mars reduced to ^"-j; in 1900-1 he made it 3 
broad, and found it quite distinct and diffuse. From Juvisy, at this time, 
I found it extremely difficult. In 1903 Molesworth judged it feeble, and 
directed toward the NNE, as had also been the case in 1886. In 1915 
Ellison drew it as directed to the NW, and broadened toward the base. 
Briault drew it as diffuse in 191 8. 

Macnes (S, 1888). Broad band, reasonably dark. It forms the border of 
the grey region to the W, and runs from Arsenius Lacus to the Lacus 
Deucalidonius. Schiaparelli noted it as broad in 1888 (Fig 144); Millo- 
chau as intense and as the border of the shaded area of Lemuria in 1903, 
when Phillips drew it as convex to the E, 3 broad, and dark. 

permessus. Streak on Uchronia, to the NE of Copais Palus. It was in- 



313 






dicated in 1856 by dc La Rue and Brodic, and I glimpsed it as broad and 
diffuse in 1900-1 (Fig 145). In 1903 Millochau and Denning drew it as 
intense. 

python (S, 1888). Band glimpsed on Cecropia by Schiaparclli in 1886 
and 1888, between Arethusa Lacus and Gcminus Fons. 

scythes. Band seen by Schiaparelli in 1888, separating the strong 
shading of Abalos from the lighter one of Nerigos. Danjon glimpsed 
traces of it in 1 920. pi ATCC 

SITON. Band separating Baltia from Abalos; it forms the border of the 
grey region, since Abalos is darker than Baltia. Schiaparelli saw it in 
1883-4 ant * '888; in 1890, it seemed to him to mark the border of the 
intense shading of Abalos. Danjon saw it as a vague, shaded-off area in 
1920. 

References 

1. Mcmoria V, p. 23. 

2. Memoria VI. p. 41. 

3. Annals of the Lowell Observatory, vol. Ill, p. 189. 

4. Mcmoria V, p. 24. 

5. Mars report for 1903, in Memoirs BAA, vol. 16, pp. 97-8. 

6. Scientific Transactions of the Royal Dublin Society, vol. 1 {2nd series), p. 30 1. 



314 



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Plate 4 Region of the Mare Stratum and the Mare Cimmerium. 



Plate 5 South and North Polar Caps. 





6 October, (a — 121 ; (p = 21 



5 November. (0 = 197°; <p = — 24 . 



4 December, co = 87 ; <p = — 13 . 



14 October. (0 = 195' ; (p - 5 




20 September, d) = 279 ; (p = — zo°. 



27 November, u — 346 :> ; (p = —25° 



Plate 6 Drawings of Mars made in 1909, by E. M. Antoniadi, with the great 

Meudon refractor, 

322 



14 November, (1) 225°; (p = — 9 



3 November, co 357*5 <P = —7° 



Plate 7 Drawings of Mars made in igri, by E. M. Antoniadi, with the great 

Meudon refractor. 

.123 




1 8 September, to = 76 J ; tp = — 17 



7 August, co = 168"; cp = — 17 



15 December, to 75°; (p = zo '■ 



1 November. u> = 148°; cp — —16° 




5 September, to 231"; <p = 16 



23 August, to = 330°; <p = -16° 



P/a/e 8 Drawings of Mars made in 1924, by E. M. Antoniadi, Kith the great 

Meudort refractor. 



324 



19 October, to - 292°; <p = —'4° 



15 September. CO 322"; <p = —12° 



Plate 9 Dratcings of Mars made in 1926, by E. M. Antoniadi, tcith the great 

Mettdon refractor. 

325 




8 February 1 929. w 95 ; (p 



if> March 1929, (0 -•• 125"; <p = I 1° 




14 December 1928. to = 270"; (p = 0° 



g December 1928. o> 330 ; tp ■ 1° 



P/alc 10 Drawing!! of Man made in 1 <j28-iq2q, by E, M. Antoniadi, uilh lite 

great Mention refractor. 



326 






INDEX 



GENERAL INDEX 



Atmosphere of Mars, 53-64; composi- 
tion of (Stoney), 66; height of, 52 
Aristotle, o b se r vation by, 13 

Canals, 18, 33-46; doubling of, +2-4; 
history of, 33ff; nature of, 33-36, 
40; perspective effects, 18, 39 

Clouds, 52-9; in ultra-violet, 59; 
white, 56-8; yellow, 3 1 , 53-6 

Dawes Limit, 15, 37-8 
Dcimos, 70-5 

Features on Mars, list of, 82-5 
Flagstaff, observations at, 18 

Lakes, nature of, 46 
I .Huh darkening, 52 
Longitudes on Mars, zero for, 8 1 
Lowell, observations by, 18, 34ff, 41 

Magnifications, use of, 16 

Mars, albedo of, 33; ancient observa- 
tions and names of, 1 1 ; brilliancy 
of, 12; climates on, 65-8; colour of, 
25; dark areas of, 26; dark areas, 
changes in, 26-9; desiccation of, 
29 _ 3o; life on?, 66-7; mountains 
on ?, 30 1 ; observation of, apertures 
needed, 14-5; orbit of, 2! ; phases 
of, 22; satellites of, 70-5; satellites, 
Mars as seen from, 74-5; sky of, 



67-8; temperatures on, 65 ■<>; vul- 

canism on, 3 1 
Mercury, 42 

Meteorological conditions for observa- 
tion, 1 cj 
Mcudon, observations at, 16, 79 

Nomenclature of Mars, 81 

Orogeny, Martian, 30-t 

1 'ho bos, 70 5 

Polar caps, 47-51; hand round, 50; 
composition of, 47; seasonal varia- 
tions in, 47-8, 50 

Proctor, map by, 87 

Ritchey, observations by, 16, 35 
Schiaparelli, results of, 44-7 
Snows, Martian, 47-9; aldebo of, 49 
Soil, nature of, 35 

Telescopes, comparison of, 17, 37 
Terminator of Mars, projections from, 
60-2 

Vegetation hypothesis, 26, 29 
Vulcanism on Mars, 31 

Water on Mars ?, 30 
Whitening under obliquity, 58 
Winds on Mars, 59-60 






1NDKXTO FORMATIONS ON MARS 



328 



Abalos, 303 
Acadinus Pons, 213 
Acampsis, 214 
Achitorum Port us, 232 
Acheron, 264 
A chillis Pons, 209 
Acidalia Depressio, 213 
Acidalium Mare, 209 
Acidalius Pons, 313 
Adamus, 264 
Adonis, 310 
Aeria, 138 
/Eolis, 249 
/Ksaeus, 265 
/Ktheria, 264 
/Ethiopia, 250 
/Kthiops 1, 265 
, Kthiops II, 265 
Aganippe Fons, 201 
A gatho daemon, 214 
Alba, 206 
Albor, 358 
Alcyonius, 365 
Alpheus, 146 
Amazonis, 358 
Ambrosia, 314 
Ambrosia: Lacus, 198 
Amenthes, 132 
Ammonii Pons, 253 
Am ph it rites Mare, 93 
Anian, 265 
Anseris Fons, 90 
An tie i Fons, 249 
Ant;eus, 266 
Anuhis, 146 
Aoniie Depressio, 183 
Aonius Sinus, 181 
Aphnitts Fons, 259 
Apis, 146 

Apodis Depressio, 108 
Apollinares Aqua;, 248 
Aquarii Depressio, 172 



Aquikv Fons, 247 

Ara, 103 

Arabia, 142 

Aram, 183 

Araxes, 215 

Arcadia, 205 

Arcti Fons, 201 

Arena, 114 

Arethusa Lacus, 137 

Arga;us, 310 

Argentus Mons, 287 

Argus Depressio, 183 

Argyre 1, [68 

Argyre 1 1 , 289 

Argyoporos, 168 

Ariadnes Depressio, 244 

Arictis Promontorium, 98 

Arimancs, 266 

Arion, 31 1 

Arius, 31 1 

Arnon, 146 

Areeris; 147 

A romatum Promontorium, 185 

Arsenius Lacus, 305 

Arsia Sylva, 200 

Arsimrs I Jepressio, i 7^ 

Artynia Fons, 360 

Ascania Palus, 359 

A scant us, 266 

Asclcpii Pons, 13 1 

Asclcpius, 147 

Ascncus Lacus, 202 

Ascuris Lacus, 206 

Asopus, 147 

Aspledon Lacus, 302 

Astabone Fons, 134 

Astabora: Sinus, 1 1 4 

Astaboras, 147 

Astapus, 147 

Astusapes, 148 

Astusapis Sinus, 1 14 

Atlantes Depressio, 245 



329 



Athyr, 149 

Attamidum Sinus, 239 
Atlantis I, 240 
Atlantis II, 240 
Auras Chersonesus, [91 
Aun-um Cornu, 184 
Aurora." F return, 175 
Aurora' Sinus, 175 
Ausonia, 87 
Ausonia Australis, 87 
Ausonia Do real is, 88 
Australe Mart', 286 
Avenus, 266 
Avionis Fons, 250 
Azania, 263 

D.vtis, 215 

Baltia, 301 

Bandusia: Fons, 259 

Bathys, 216 

Dathys Portus, 181 

Dibits Fons, 259 

Bona Spei Promontorium, 263 

Borbyses, 149 

Borea Depressio, 310 

Boreas, 266 

Boreosyrtis, 149 

Boreum Mare, 209 

Boreus Pons, 132 

Bosporium Promontorium", 180 

Bosporos Gemniatus, 179 

Botrodi Fons, 131 

Bucoleontis Portus, 93 

Cadmus, 311 

Caltrrhffi, 149 
Calirrhces Fons, 138 
Caliri-hces Sinus, 213 
CaJydon, 216 
Cambyses, 267 
Cam pi Phlegnei, 170 
Candor, 188 
Can is Fons, 201 
Canopi Fons, 201 
Cantabras, 216 

330 



Capri Cornu, 177 

Caralis Fons, 235 

Casius, 150 

Casta! ia Fons, 253 

Castorius Lacus, 260 

tYbrenia, 263 

Cecropia, 308 

Ccdron, 31 1 

Centauri Lacus, 88 

Cephissus, 3 1 1 

Ceraunius, 216 

Cerberi Fons, 25 1 

Cerberi Sinus, 244 

Cerberus I, 267 

Cerberus I], 268 

Cerberus III, 269 

Ceti Lacus, 189 

Chalce, 168 

Chaos, 269 

Charitum Promontorium, 170 

Chersonesus, 86 

ChimaTa.- Depressio, 239 

Chironis Fretum, 290 

Choaspes, 3 1 1 

Chronium Mare, 231 

Chrysas, 216 

Chrysc, 184 

Chrysokcras, 180 

Chrysorrhoas, 217 

Cimmeria Insula, 244 

Cimmerium Mare, 240 

Circa-urn Promontoriuni, 89 

Claritas, 217 

Clarius, 217 

Cocytus, 270 

Colo.' Palus, 133 

Columba; Fons, 200 

Copals Palus, 133 

Coracis Portus, 180 

Corona: Fons, 90 

Corvi Lacus, 200 

Crateris Depressio, 183 

Crocea, 108 

Crucis Fons, 249 

Cyane Fons, 205 







Cyclopia, 250 
Cyclops, 270 
Cyclopurn Fons, 250 
Cyclopum Sinus, 243 
Cydnus, 31 1 
Cydonia, 145 
Cyllenius Lacus, 125 

Da-dalta, zoo 

Dan aid urn Depressio, 232 

Daphnes Depressio, 122 

Dardanus, 217 

Delphini Portus, 179 

Dcltoton Sinus, 115 

Deucalidonius Lacus, 306 

Deucalionis Regio, i°i 

Deuteronilus, 151 

Dia, 290 

Diacna, 261 

Diana- Fons, 249 

Dinscuria, 144 

Dirce Fons, 144 

Dium Promontorium, 103 

Doradus Depressio, 183 

Dori Depressio, 99 

Draconis Promontorium, 249 

Dryad is Palus, 235 

Dryas, 271 

Echus Lacus, 190 

Eden, 143 

Edom, 140 

Edom Promontorium, 141 

Electris, 235 

Elysium, 257 

Endoris Fons, 209 

Engedii Fons, 209 

Enipeus, 311 

Eos, 174 

Eosphon Lacus, 198 

Eosphoros, 217 

Erebus, 271 

Eridania, 236 

Erigonc, 3 1 1 

Erinnys, 272 



Erythra. 1 Depressio, 178 
Erythneum Mare, 171 
Eumenides, 272 
Eunostos I, 272 
Eunostos II, 273 
Euphrates, 151 
Euphratis Lacus, 142 
Eurotas, 273 
Euripus I, 152 
Euripus II, 152 
Euryalus, 152 
Buxtnus Lacus, 259 

Fama.- Depressio, 23 1 
Fastigium Aryn, 141 
Felis Promontorium, 194 
Ferentina.- Lucus, 259 
Fevos, 273 
Flora- Fons, 249 
Fortuna, 217 
Frigoris Fons, 308 
Fulgoris Depressio, 198 
Fusea I >t-pressiti, 239 

Galaxias, 273 
Gallinaria Sylva, 201 
Ganges, 218 
Gangis Sinus, 177 
Gehon I, 152 
Gchon II, 218 
(ierninus Fons, 308 
Gcryon, 218 
Giguntum Sinus, 239 
Gigas, 274 
Gordii Nodus, 252 
Gorgon, 274 
Gorgonum Sinus, 239 
Granicus, 275 
Grus, 275 
Gyndes, 275 

1 lades I, 275 
Hades II, 276 
lladria, 153 
Hadriacum Mare, 90 



331 



1 latex, 2 1 S 

Hammonis Cornu, 140 

Hebes Ladus, 190 

1 lebrus, 3 1 1 

liecates Lacus, 257 

1 leiiconius, 153 

I Id 1 ; Dcprcssio, 198 

Hellas, 90 

1 Idles Dcprcssio, 95 

lirlk'sponticif Dcprcssio, 2S6 

I Idlespontus, 94 

I lepha , stus, 270 

Ilereeum Prornontorium, [94 

Hcrculis Column if, 276 

Hcrculis Fons, 261 

Ilcspcri Sinus, 243 

Ilcspcria, 245 

I lesperus, 277 

Hibcs Fons, 253 

I [id debet, 154 

I 1 1 p ) > L 1 1 1 ! S . 312 

H° r . "55 

I lomnua Prornontorium, 170 

I lybLt-iis, 277 
] lydaspes, 218 
Jlydaspis Sinus, 173 
Hydra: Pahis, 185 
Hydraotcs, 221 
Hyllus, 1 55 
Hypela-i Fons, 259 
Hyperboreus Lacus, 303 
Hypcrnotius Mons, 299 
Hyria Lacus, 246 
I lyscus, 2Zi 

liini Fretum, 172 
lani Sinus, 172 
lapcti Insula, 1 18 
lapygia Viridis, 104 
laxartes, 312 
Icana, 233 
Ida 1 us Fons, 207 
Idalius, 313 
Icmc, 306 
Ilissus, 313 



332 



Incurva Insula, 106 

Indus, 22 1 

Insula Sacra, 187 

I < m km Dcprcssio, 104 

Ionium Marc, 104 

los Insula, 239 

Iris, 223 

I siil is Regio, 126 

Ismenia, 136 

Ismcnius Lacus, 134 

Issedon, 223 

Istcr, 223 

I us Lacus, 190 

Ixion, 155 

Jamuna, 223 
Jamuna; Sinus, 177 
Jordanis, 224 
Jordan is Fons, 209 
Jovis Lacus, 203 
Jubar, 248 
Juvenra: Fons, 187 

Kison, 313 

Labeatis Lacus, 207 

Labotas, 155 

Lsestrygon, 277 

Ljestrygonum Sinus, 243 

Leda; Fons, 108 

I .L-rnuria, 307 

Lethe, 278 

Libya, 123 

Lib yea- Paludes, 126 

Lucis Tortus, 19S 

Lumen, 247 

Lunic Lacus, 186 

Lupi Fons, 249 

Lux, 200 

I. yds, 278 

Lynca-us, 278 

Lyra; Fons, 249 

Mifotis Fa I us, 303 
Magna Dcprcssio, 298 






Magnes, 313 

Malea Prornontorium, 93 
Marcotis Lacus, 203 
\l;irgaritifer Sinus, 172 
Maricit Lucus, 253 
Medusa- Fons, 248 
Mclas Lacus, 189 
Mcmnonia, 246 
Meridian i Sinus, 1 18 
Mens Insula, 132 
Mc ropes Dcprcssio, 233 
Mesogaa, 247 
Minos, 278 

Mnemosynes Fons, 263 
Moab, 141 
Moris Lacus, 125 
Morpheos Lacus, 257 

Nasamon, 155 
Nectar, 224 
Nectaris Fons, 194 
Nectaris Sinus, 177 
Neith Rcgio, 129 
Nepenthes, 156 
Ncphclcs Dcprcssio, 233 
Nerei Dcprcssio, 94 
Xereidum Prelum, 170 
Nerigos, 303 
Neudrus, 157 
Nia, 225 
Nieenus, 157 
Nili Lacus, 132 
Nili Pons, 1 15 
Nili Ponus, ,133 
Nili Sinus, 1 14 
Niliacus Lacus, 207 
Nilokcras, 225 
Nilosyrtis, 157 
Nilus, 226 
Nix Atlantica, 127 
Nix Cydonia, 145 
Nix Olympica, 204 
Nix Hcsperia, 123 
Nix Tanaica, 207 
Noachis, 95 



Noctis Lacus, 190 

Nodus Alcyonius, 1 29 

Nodus Gordii, 252 

Noti Sinus, 294 

Notus, 294 

Novissima Thyte, 295 

Novus Mons, 286 

Nox, 226 

Nympha-uin Prornontorium, 139 

Qceanidum Marc, 168 

Getsntis Dcprcssio, 172 

IFnotria, 105 

Ogygis Regio, 178 

Olympia, 309 

Olympia: Depressio, 122 

Omphales Fretum, 131 

Ophir, 188 

Ophiuchi Sinus, coo 

Orcus, 278 

Oresciadum Dcprcssio, 245 

Orion, 159 

Orontes, 159 

Ortygia, 301 

Osiridis Prornontorium, 124 

Oti Lacus, 200 

Oxia, 1 84 

Oxus I, 226 

Oxus II, 160 

Pactolus, 279 
Palinun Fretum, 231 
Palinuri Sinus, 231 
Pambotis Lacus, 256 
Pancha'ta, 307 
Pandora; Fretum, 98 
Parncs, 160 
Parva Dcprcssio, 299 
Pavonis Lacus, 201 
Fcneus, 161 
Pcra-a, 89 
Permessus, 313 
Phathontis, 234 
Pharos Insula, 140 
Phasis, 227 



333 



I'hison, 161 

I'hlegethon, 279 

Phlegra, 262 

Phrcbi Dcpressio, 198 

Phcenicis Lacus, IV'} 

Phrixi Regio, 180 

Phrygius Lacus, 253 

Pierius, 162 

Piscis Dcpressio, 183 

Pityusa Insula, 93 

Plutus, 279 

Pontica Dcpressio, 180 

Poros, 162 

Posodium Promantnrium, 89 

Pracyonis Depressio, [07 

Promethei Sinus, 295 

Propontis I, 260 

Propontis II, 261 

Protei Regio, 178 

Protonilus, [63 

Pscboas Lacus, 133 

Pyramus. [64 

Pyriphiegethon, 279 

Pyrrha: Regio, 174 

Python, 314 

Rhyndacus, 280 
Rtma Angusta, 299 
Rima Austral is, 298 
Rima Borcalis, 310 
Rima Brevis, 298 
Rima Tenuis, 310 

Sabwus Sinus, 1 16 
Sacra Insula, 187 
Scaniandcr, 280 
Seaman dri Sinus, 243 
Scandia, 305 
Scheria Insula, 213 
Scorpit Palus, 250 
Scotitje Frvtum, 252 
Scylla and Charybdis, 100 
Scythes, 3 1 4 
Semiramidis Lacus, 142 
Serpentis Mare, 99 

334 



Scxtantis Dcpressio, 172 

Sigcus Portus, 1 1 8 

Siloe Fons, 143 

Simeontis Sinus, 232 

Simois, 280 

Sirbonis Palus, 140 

Sirenius I, 281 

Sirenius II, 282 

Sirenum Dcpressio, 240 

Sirenum Mare, 236 

Sirenum Promontorium, 247 

Sirenum Sinus, 238 

Sirii Fons, 201 

Sirus, 228 

Sisyphi Dcpressio, 298 

Sitacus, 164 

Sithonius Lacus, 263 

Siton, 314 

Soils Lacus, 195 

Somni Deprcssio, 295 

Sphingos Lacus, 143 

Strongylc Insula, 103 

Stygis Lacus, 255 

Stymphalius Lacus, 263 

Styx, 282 

Symplegadcs Insula-, 244 

Syrtis Major, 109 

Syrtis Minor, 108 

TanaTs, 228 
Tantalus, 283 
Tartarus, 283 
Tauri Pons, 194 
'IVnipe, 206 
'Pharsis, 201 
1'baumasia Fcelix, 192 
Thermodon, 283 
Thoth I, 164 
Thoth II, 165 
Thyle I, 291 
Thyle II, 293 
Thytes Collis, 294 
Thyles Moris, 292 
Thymbrse Fons, 263 
Thymiamata, 183 



Tiphys Fretum, 233 
Titan I, 283 
Titan II, 284 
Titanum Fretum, 259 
Titanum Sinus, 239 
Tithonius, 22S 
Tithonius Lacus, 188 
Tractus Albus, 201 
Triton, 165 
Tritonis Lacus, 126 
Tritonis Sinus, 244 
Trivii Fretum, 255 
'Privium Charontis, 253 
Tuderis Fons, 213 
Tyndaros, 229 
Typhon, 166 
Typhonii Sinus, 1 is 
Tyrrhcnum Mare, 106 

Uchronia, 307 

Ultimum Promontorium, 292 

Ulysses, 229 

Ulyxis Fretum, 293 

L'mbra, 129 



liiinia; Pons, 253 
U rani us, 229 
liopia, 130 

Vesta- Deprcssio, 198 
Yorticis Dcpressio, 239 
VukaoJ Pelagus, 171 
V'ultur, 284 

Xantbe, 185 
Xunthi Sinus, 232 
Xanthus, 284 
Xcnius, 166 
Xisuthri Regio, 118 
Xuthi Dcpressio, 99 

Yaonis Fretum, 94 
Yaonis Regio, 94 

Zea Lacus, 93 
Zcphyri Fons, 24X 
Zcphyria, 248 
Zephyrus, 285 



INFRARED - THE NEW ASTRONOMY 

David Allen 

The first book to bring together in one place all the important 
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EXPERIMENTS IN ASTRONOMY FOR AMATEURS 

Richard Knox 

Explains how the amateur astronomer and school/college student can 

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THE PLANET MERCURY 

E.M. Antoniadi 

Translated from the French by Patrick Moore 

Of immense historical and scientific interest, appeared in French in 
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THE YOUNG ASTRONOMER AND HIS TELESCOPE 

Patrick Moore 

Here Patrick Moore answers the questions most often asked of him: 
How do I start taking an interest in astronomy? Where can I buy a 
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THE COMETS: VISITORS FROM SPACE 

Patrick Moore 

A review of all aspects of these strange, ghost-like members of the Sun's 
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